CN1659020A - Particulate material having multiple curable coatings and methods for making and using same - Google Patents

Abstract

The present invention relates to coated particulate matter wherein the particles are individually coated with a first set of one or more layers of a curable resin, for example, a combination of phenolic/furan resin or furan resin or phenolic-furan-formaldehyde terpolymer, on a proppant such as sand, and the first set of layers is coated with a second set of one or more layers of a curable resin, for example, a novolac resin with curative. Methods for making and using this coated product as a proppant, gravel pack and for sand control are also disclosed.

Description

Granular material containing multi-layer curable coating and its preparation method and application

I. Application documents

This application claims priority to U.S. Provisional Patent Application No. 60/385,578, filed June 5, 2002, and U.S. Provisional Patent Application No. 60/384,419, filed June 3, 2002, both of which are in their entirety Incorporated herein by reference.

II. Fields of Invention

A. Background of the invention

The present invention relates to encapsulated particulate material wherein the particles are individually encapsulated by a first set of monolayer or multilayer curable resins (e.g. combinations of phenolic and furan resins, furan resins, phenolic-furan-formaldehyde trimers) on a proppant (eg, sand), while the first set of coatings is overlaid by a second set of single or multiple layers of a curable resin (eg, novolac resin). The invention discloses a preparation method and usage of a package product which is used as a proppant or gravel filling and can be used for sand and gravel control.

B. Detailed description

The term "proppant" refers to a particulate material that is injected into formation fractures around oil, gas, water, and other similar boreholes to support and keep the fracture open for gas or liquid to flow through the fracture drilling.

U.S. Patent No. 4,694,905 (to Armbruster), incorporated herein by reference, discloses a cured particulate material in which the particles are wrapped by a cured combination of phenol resin and furan resin or a furan trimer resin, respectively, in a proppant (for example, sand) forms a pre-cured resin coating on the surface, a continuous coating based on phenolic pre-curing, thereby substantially improving the chemical resistance properties of the proppant. Another embodiment of the invention involves the application of multiple layers of resin over the particulate material, resulting in a layered coating that ultimately contains the desired amount of cured resin.

U.S. Patent No. 4,722,991 (to Armbruster), incorporated herein by reference, discloses a trimer prepared from phenol, furfuryl ethanol and formaldehyde, wherein the basic amount of furfuryl ethanol is A valent metal salt catalyst, a catalytic reaction occurs, wherein the reaction is substantially carried out under aqueous conditions.

U.S. Patent No. 4677,187 (to Armbruster), incorporated herein by reference, discloses a furfuryl alcohol formaldehyde resin that can be prepared using a water-soluble polyvalent metal salt as a catalyst.

U.S. Patent Application No. 5,837,656 (to Sinclair et al), incorporated herein by reference, discloses a resin-encapsulated proppant particle comprising a particle matrix, an inner coating of curable resin, an outer coating of cured resin, coating. These resin-coated particles are prepared by first coating the substrate with a reactive resin; then, coating the inner curable resin layer with a second coat or outer coat at sufficient temperature and for a sufficient time Allows the outside coating to cure while the inside coating remains curable.

Typically, proppants are used during hydraulic fracturing to support and keep open fractures formed in formations, such as oil and gas wells. These proppants can be in a pre-cured or curable state. Pre-cured proppants are set before being added to the formation. Curable packs are solid proppant packs that form a solid proppant pack after settling downhole. Typically, resin components used as curable coatings on the surface of a proppant substrate (sand, ceramic, etc.) will form a highly cross-linked coating on the surface of the substrate. Although the thermal properties of the coating can be optimized, optimal conditions are not required for the importance of the coating in the oil field industry, where the operating temperature of the coating will generally not exceed 400°F, but the coating will be affected. Stress that breaks weak bonds.

Curable phenolic resin coated sand can be used as a proppant and is commercially available. Curable phenolic resin coatings contain at least partially but not fully cured phenolic resin, in contrast, the term "pre-cured" refers to phenolic resin coatings that are already cured and are commercially available.

Another aspect of obtaining products from a formation is that in order to extract hydrocarbons, such as natural gas and crude oil, from the formation, wellbores need to be drilled into the production zone that hosts the hydrocarbons. However, the production of oil, gas and water from soft or less solid rock formations usually produces sand grains of rock along with the production fluids. The produced sand and gravel follow the well fluid, causing serious problems such as erosion of underground working faces and surface production equipment and accumulation of sand and gravel in wellbore and surface separators. Various methods such as gravel packing, screening and plastic cementation have been employed over the years with varying degrees of success. However, these methods suffer from various technical and compositional limitations. Sand control is discussed in greater depth in US Patent No. 6,364,019, the contents of which are incorporated herein by reference.

In order to maintain the production rate of the wellbore and control the flow of hydrocarbons produced from the wellbore, a variety of prior art equipment and systems have been used to prevent the collapse of the wellbore caused by natural forces and to prevent the natural forces from convecting the flow of liquid through the wellbore. blockage and interruption. A system in the prior art provides a full-depth hole formwork for a wellbore, in which the wellbore wall is lined with steel casing, and concrete is added to the annular space between the outer surface of the casing and the wellbore wall to ensure the safety of the wellbore wall . Thereafter, ballistic or pyrotechnic equipment is used to penetrate the steel casing and the surrounding concrete annular gap to connect the production area, so that the required hydrocarbon fluid flows from the production layer into the casing interior. Typically, the inside of the casing is hermetically sealed above and below the production section, thereby sealing small-diameter production tubing through the upper layer to provide a clear, clean artesian conduit for hydrocarbon fluids to the surface.

Another completion system protects the integrity of the wellbore by tightly packing sand, gravel, or a combination of both between the original wellbore and the production tubing, thereby avoiding production thousands of feet from the surface The time and cost of laying steel casing in the area. The gravel pack is inherently permeable to the required hydrocarbon fluids and reinforces the wellbore structure not only to avoid internal collapse but also to withstand fluid washout. This completion system is known as an "open hole" completion. The device and method for placing wrapped gravel deposits between the well wall and the production pipeline belong to the "open hole gravel packing system". There are prior art open hole gravel packing systems that can be used to place and pack gravel in hydrocarbon production zones; unfortunately, due to wellbore pressure fluctuations along the production zone, this system was found to have a significant risk of accelerating borehole wall collapse. risk. The pressure fluctuations described above are caused by the surface operation of downhole tools placed in the circulation of the steering fluid in the well and the laying of pipes along the route. Gravel packing is discussed in more depth in US Patent No. 6,382,319, the entire contents of which are hereby incorporated by reference.

Accordingly, there remains a need to provide improved particles for use as proppants, gravel packs, and/or sand control in formations.

III. SUMMARY OF THE INVENTION

The present invention relates to encapsulated particulate materials wherein particles of a proppant matrix, such as sand, ceramics, are individually encapsulated by two or more curable coatings, wherein all coatings on the surface of the particles are in a curable state. Each coating contains a different composition, and the present invention generally includes wrapping the surface of the proppant matrix with an inner coating comprising at least a single layer of a curable resin, followed by an outer coating comprising at least a single layer of a second curable resin. Coated wrap. "Different compositions" refer to resins with different chemical formulas, rather than resins with the same chemical formula but different degrees of cure.

In this specification, the terms "cured" and "curable" are defined using three experiments historical in the industry and used to determine the state of the inside coating and the outside coating.

(1) Temperature experiment of sticking point: the wrapped material is placed in a heating melting point tank, and then the lowest temperature of the wrapped material strip is measured. Based on the resin system used, a "bar temperature" greater than 350°F is generally considered a fixed material.

(2) Acetone extraction rate experiment: as described below, an acetone extraction method for dissolving unfixed resin fragments.

(3) Compressive strength test: After wet compression at 1000 psi and 250°F for 24 hours, the coated particles were neither combined nor hardened, indicating that a cured material was used.

However, unless otherwise stated, the terms "curable" and "curable" are acetone extraction experimental definitions.

In a specific embodiment, the encapsulated particles have a first inner coating comprising a furan resin, a curable combination of a phenolic resin and a furan resin, or a curable furan trimer resin, forming at least one single layer of the proppant matrix encapsulating the proppant matrix. A curable coating of one layer; and an outer coating of at least a single layer containing a phenol formaldehyde novolac resin, thereby providing a curable proppant containing a curable inner layer (single layer) suitable for adding to the formation in a curable state or multiple layers) and a curable outer layer (single or multiple layers). The invention also includes embodiments of various outer and/or inner coatings, for example, two inner coats of a curable resin, such as furan trimer, applied to the substrate, and three inner coats applied to the surface of the inner coat. A curable resin coating, such as phenol, formaldehyde, novolac. However, the sequence and number of resin coatings are not particularly limited. Furthermore, it is considered within the scope of the invention to use any curable resin for the coating. For example, any thermosetting resin, such as epoxy resins, modified phenolic resins, urethane resins, and all resins disclosed in U.S. Patent No. 4,585,064 (to Graham et al, the entire contents of which are hereby incorporated by reference), can be used. As a curable resin for interior and exterior coatings.

The present invention also relates to a method for preparing a curable proppant containing only a curable coating, comprising the steps of encasing a particle matrix with at least a single layer of a curable inner coating to form a curable resin coating on the surface of the proppant matrix , the above-mentioned inner coating can include, for example, a curable furan resin, a curable combination of a phenol (resole phenol) resin and a furan resin, or a curable phenol-formaldehyde-furan trimer resin; A second coating of at least a monolayer of cured resin surrounds the particle matrix. When multiple coats are used, reduce the coating temperature of the coating to the conventional temperature at which the coating is applied.

The temperature, curing agent level and concentration, catalyst level and concentration, and other factors are specifically selected to provide a viable cycle time while preventing full cure of the resin coating. The temperature, catalyst or other curing agent and its concentration are generally selected for partial conversion of the reactive resin, but not for total conversion of the reactive resin.

For example, the substrate may be heated to about 400-550°F or 400-530°F, typically 400-410°F or 405-410°F, before the heating is turned off, before applying the different resin coatings. Likewise, the temperature of the substrate (including any resin applied to the surface of the substrate) during the coating process can be in the range of 250-550°F. The temperature at which the substrate is heated can be specifically chosen so that the resin melts so that the resin sufficiently coats and moistens the substrate. In addition, the temperature must be limited so that the resin does not collapse or thermally degrade, so that the curing of the resin can be precisely controlled.

The concentration of curing agents (such as catalysts or crosslinkers) can be reduced by a factor of 4, from about 25% conventional catalyst concentration for conventional pre-cured proppants or conventional curable proppants, to only partially affecting the inner furan, resole Concentration converted; the amount of curing agent used for the second furan coating was reduced by a factor of 2. As mentioned above, the amount of curing agent can be adjusted to achieve any desired degree of cure as long as the resin remains in its curable state. In at least some embodiments, when curing agents are used downhole, as a result of using particularly low levels of curing agent, the resin does not crosslink like conventional curable proppants or conventional precured proppants from which it is composed.

The definition of the product is elastic is that the product can withstand the standard cyclic load test of 30 cycles and the reflow rate is less than 15%.

Low enough levels of curing agent can be used so that the reactive resin (once placed in the ground) is eventually converted into a lightly cross-linked elastomeric coating that provides other excellent properties. For example, the pellets can be heated above 400°F, and the concentration of the catalyst can range from 0.05 to 0.25% by weight based on the weight of the furan resole resin; -15% by weight.

In one embodiment, furan resin, any combination of resole and furan resin, or any trimer of phenol-furan-formaldehyde may be used as an inner coating when the particle temperature ranges from 380°F to 450°F ; When the particle temperature is in the range of 200-300°F, any top coat of novolak can be used. However, when the temperature of the substrate is outside this range, the amount of crosslinker (or catalyst) can be adjusted to achieve the desired degree of cure. For example, when adding a novolak resin system, if the temperature of the substrate is 500°F, for example, diluting the hexa(hexamethylenetetramine) solution with water will reduce the degree of cure. Similarly, when adding a furan-formaldehyde undercoat, if the substrate temperature is only 350°F, the amount of catalyst acid can be increased to increase the degree of cure of this coating. Therefore, it can be concluded that by adjusting the content of crosslinking agent corresponding to different temperatures, a wide range of curing degrees can be achieved. Thus, the method of the present invention is applicable to a wide range of operating temperatures.

Additionally, the catalyst content used for the resole and furan undercoats is reduced by 98%, typically 75%, compared to the conventional catalyst content of the pre-cured coating. On a dry-solvent-free basis, the catalyst content for the undercoat is in the range of 0.05-0.25 wt%, such as 0.1-0.15 wt%, based on the total weight of the coating resin.

The level of hexamethylenetetramine crosslinker (also known as "hexa") in the topcoat is reduced by 70-90% compared to conventional novolak coatings. Thus, on a dry-solvent-free basis, the hexavalent content for the topcoat is in the range of 1-5 wt%, such as 3-4 wt%, based on the total weight of the resin used in the coating.

The present invention also relates to the preparation and use of a proppant comprising a plurality of coatings of curable resin coated on the surface of a particulate material to form a final multilayer coating containing the desired amount of curable resin .

The present invention also addresses the need for elastic coatings with sufficient thermal properties.

However, the present invention not only accomplishes this task, but also achieves unexpected potential advantages, as described below, under the condition of elevated temperature during the slurry experiment, even when exposed to aqueous media, the defined resin encapsulation material has enhanced bond strength Ability. Furthermore, the inventors believe that as the oil or gas flushes the fracture open, the pressure (weight) on the proppant increases when the well is producing and decreases when the well is shut down. Thus, after the curable proppant solidifies, creating a consolidated proppant pack, the wellbore is subjected to cyclic stresses and/or strains that fracture the strong proppant pack and cause reflow of the broken proppant pack, either It can be a single particle or a consolidated particle group.

However, the plurality of curable coating particulate materials of the present invention have some ability to recombine after being placed and cured in the formation and subjected to cyclic stress. Thus, if a robust proppant pack containing the proppant of the present invention fractures during well production, the well operator can shut it in and allow the particles to recombine with each other.

The proppants of the present invention exhibit improved rebonding capabilities over conventional proppants. The free compressive test (UCS) of the resin-wrapped proppant was carried out to measure its recombination ability; according to the detailed records of the UCS test standard, the compressive strength value was determined. In the experiment, repeated rubbing was used using a metal screen (20 mesh) to break up solid pieces of material into individual particles until substantially individual particles were recovered. These particles were rescreened to isolate the desired size range (ie 20/40). The sieved granules were again subjected to a free withstand voltage test as described in the text. The UCS value is determined and compared to the initial strength values recorded for these particular resin-coated proppants. The reassociation strength was reported as a percentage of the initial UCS-association strength.

It is advantageous to have the ability to reassociate. "Previously curable" proppant particles that have been dislodged from the proppant pack can be recombined into the proppant pack due to their ability to recombine before being sent out of the formation. This was an unexpected phenomenon, since it was assumed that after curing the curable particles no longer retained appreciable reassociation ability.

Another potential advantage of having multiple curable coating particle materials is that bond strength can be preserved. Bond strength retention was determined by first measuring a sample of proppant by unrestricted compressive strength (UCS) testing as described in the section titled "Parameters of Encapsulated Particles" in the text, and then, taking a second sample of proppant After performing the "slurry test", the retention of the proppant's initial UCS was determined.

In the slurry test, first, a sample of resin-coated particles was subjected to a free compressive strength (UCS) test as described below. Another sample of the resin-coated particles is then added to a 2% aqueous solution of KCl at a rate of 12 pounds of particles per gallon of KCl solution, followed by heating to 200°F for an additional time, such as 1, 2, or 3 hours. Finally, the pellets were recovered and tested for unrestricted compressive strength (UCS) as described below. The retention of bond strength is illustrated by comparing the UCS values of the samples obtained after the heated slurry test with the UCS values of the samples obtained before the slurry test. The retention of bond strength was recorded as a percentage of the initial value before the sample was exposed to the heated slurry test (ie UCS value after the slurry test/UCS value before the slurry test x 100%). After slurry testing, the coated particles of the invention have a compressive strength of at least 60%, preferably at least 70%, 80% or 90% of the initial compressive strength. Most preferably, the compressive strength of the coated particles of the invention after the slurry test is 100% of the initial compressive strength. This demonstrates that the coated particles of the present invention have excellent retention of initial bond strength.

Advantageously, the present invention can not only provide a high ratio of bond strength retention, but also have a very high UCS value after the slurry test, such as a UCS value of at least 500 psi, 1000 psi, or 1500 psi.

It is advantageous to have high retention of binding strength. Typically, the packaged proppant is transported to its destination by truck or other means of transportation, and then pumped into the well. After delivery, the proppant particles must function by themselves, and are hydraulically transported into the fracture. Typically, this step lasts 6 hours or more. Correspondingly, the slurry experiments illustrate the bond strength of the resulting proppant pack after these steps. The high bond strength retention indicates that the particles did not lose their potential to form consolidated proppant packs during transport. The low bond strength retention indicates that a particular proppant composition lost its ability to form a consolidated pack during run-in when compared to its pre-transportation strength potential.

In other words, these multiple coatings did not fully cure prematurely under conditions normally associated with the initial location of proppant addition to the formation. Thus, the proppant retains its bonding potential after being subjected to the stresses encountered within the formation in which it was originally placed. Typically, 1-4 hours are required to achieve any measurable bond strength, based on the temperature and chemical composition encountered. Therefore, multiple coatings did not cure prematurely in the well.

The present invention also provides a resin-encased oilfield proppant that has an unexpected tolerance limit, even when subjected to occasional cyclic stresses, and continues to prevent flowback from the formation. For example, when a well is turned on, pressure builds up within the formation, helping to keep open fractures containing strong proppants. However, when the well is shut in, the hydraulic pressure decreases and the fracture further squeezes the strong proppant in the fracture. Prior to this development, cyclic compressive stress had caused production decline, or proppant flowback from the formation, which (1) reduced hydrocarbon production through fractures, and (2) caused surface problems such as proppant flowback into carbon Production equipment for hydrogen compounds. As described in the section entitled "Encapsulated Grain Parameters," cyclic stress experiments determine how a consolidated proppant pack responds to stresses and movements induced by the formation during normal operation. These all involve repeated start-up and shut-down of wells resulting in displacement within the formation or other natural phenomena. It is necessary to provide proppants that are more resistant to this stress.

Another potential advantage of the proppant of the present invention is that the curing of the overcoat can be controlled such that bond strength develops under conditions of closure stress in the fracture, but not in the wellbore when subjected to hydrostatic pressure alone (no differential stress). Develops bond strength; proppant withstands elevated hydrostatic pressure in the wellbore with minimal closure stress. Thus, if desired, proppant can be removed from the wellbore by maintaining downhole conditions in the absence of differential stress for a period of time.

Another potential advantage of the proppant of the present invention is that it can still maintain the ability to be cured even if it is stored in a high-temperature natural environment. In parts of the world that experience very hot weather, proppants can be stored for extended periods of time at temperatures as high as 140°F. During this high temperature storage, premature curing of the curable proppant can result, which results in a partial loss of curability and a simultaneous loss of potential bond strength after injection into the downhole formation. On the contrary, the present invention can withstand high temperature storage, and after 14 days at 140 ° F, the coated particles have at least 80% or at least 90% compressive strength retention according to UCS test, preferably at least 95% compressive strength retention. Compression retention. Typically, proppants of the present invention can withstand such high temperature storage, and after storage at 140°F for 28 days, the encapsulated particles have a compressive strength retention of at least 80% or at least 90%, preferably at least 95%, as determined by the UCS experiment. compressive strength retention.

IV. Detailed Description of the Drawings

This cross-sectional view shows a conventional coated particle of the present invention.

V. Detailed Description of the Preferred Embodiments

The present invention provides a coated particle comprising a matrix coated with at least a single layer of a curable resin coating. The curable resin coating can be selected from phenol-formaldehyde resin, epoxy resin, urea-acetaldehyde resin, furfuryl alcohol resin, melamine-acetaldehyde resin, polyester, alkyd resin, respectively.

Typically, the coated particles of the present invention comprise at least one inner coating layer comprising furan resin, a combination of furan resin and phenolic resin, or a phenol-furan-formaldehyde terpolymer resin, respectively.

Additionally, the coated particles of the present invention comprise at least one resinous outer coating comprising a curable phenol-formaldehyde-novolak resin.

The present invention also provides a method for preparing coated particles comprising only a curable coating, wherein at least a single layer of an inner curable resin coating and at least a single outer coating of a curable resin are used to coat sand or other particulate substrates .

A. Matrix

The particulate material used in the present invention can be any solid material normally used as a proppant. For example, suitable particulate materials include sand, natural mineral fibers such as zircon, mullite, ceramics such as sintered ceramsite, or sintered alumina, other non-ceramic refractory materials such as grinding balls, glass balls. The individual particles of the particulate matrix have a particle size range of US Standard Laboratory mesh number 8-100 (ie, mesh size of about 0.0937-0.0059 inches). Preferred substrates have a diameter in the range of 0.01-0.04 inches. Unlike alumina, ceramsite contains natural impurities and therefore does not require the addition of sintering agents. Ceramsite is a commonly used proppant particle. Therefore, ceramsite is both hard and resistant to deformation. Deformation is not the same as crushing which causes particle damage. In addition, the substrate will not melt below 200°F or 225°F, and generally, the substrate will not melt below 450°F or 550°F.

However, it can be determined that the additional addition of deformable water-insoluble granular materials and non-deformable water-insoluble granular materials falls within the protection scope of the present invention. The deformed particles are described below.

In addition, it is recognized that at least a single layer of a curable inner coating and at least a single layer of a curable outer coating are coated on the surface of other particulate materials, such as particles used in sand control and gravel packing, as described herein, and Realizing the cohesive strength between particles under pressure belongs to the protection scope of the present invention.

B. Curable resin

A curable resin as used in the present invention is any resin capable of enveloping a substrate in an uncured form. Examples of such resins include phenol-acetaldehyde resins, melamine resins, resole and novolak resins, urea-acetaldehyde resins, ethylene oxide resins, furfuryl resins, and urethane resins.

The resin can be used in a curable state, and even if a curing agent for accelerating curing, such as a catalyst or a crosslinking agent, is added, the resin still has curable ability.

A common test used to determine curing capacity is the acetone extraction rate test, as described in the section titled "Wrapped Proppant Parameters".

However, it will be appreciated that the curable state for encapsulating the matrix is a process parameter and not a function of the resin itself. In particular, the temperature at which the resin is applied and the amount or concentration of curing agent added can effectively determine the level of "curability" of the resin.

1. Furan resin

In one embodiment, furan resin is used. Furan resin is a thermosetting resin produced by the reaction of furfuryl alcohol and formaldehyde, or the self-polymerization of furfuryl alcohol, or a combination of the two reactions.

Furfural can also be used instead of furfuryl ethanol.

In the process of adding water-soluble polyvalent metal salt as a catalyst, furfuryl alcohol-formaldehyde resin is prepared. The use of water-soluble polyvalent metal salts eliminates the possibility of using protic acid catalysts, and the reaction proceeds essentially under aqueous conditions.

The preferred form of formaldehyde is 50% formaldehyde in water. However, other grades of formaldehyde can be used as well. Paraformaldehyde can also be used if sufficient water is added to the reactants to keep all or most of the curing agent in solution.

Furfuryl ethanol, formaldehyde and polyvalent metal salt catalysts can be directly added to the reaction vessel, and then heated to the reaction temperature.

The water-soluble polyvalent metal salt catalyst used in this reaction contains polyvalent metal ions of manganese, zinc, cadmium, magnesium, cobalt, nickel, copper, tin, iron, lead and calcium. Preferred catalysts are zinc acetate, lead acetate, or mixtures thereof.

In the reaction of furfuryl ethanol, aqueous formaldehyde and polyvalent metal salt catalyst, it is necessary to remove excess water, including the excess water produced by the condensation reaction, and the water contained in the aqueous formaldehyde exceeds the amount required for dissolving the catalyst. During the reaction, water can be removed by distillation, which can increase the reaction rate and reduce the water content of the final product. Water removal may conveniently be accomplished during the course of the reaction or at any point that facilitates product processing.

An important limitation in removing water content during the reaction is to ensure that there is sufficient water to dissolve a sufficient amount of polyvalent metal salts in the aqueous solution to catalyze the reaction between furfuryl ethanol and formaldehyde. Undissolved catalyst cannot effectively catalyze the reaction. Therefore, there should be enough catalyst in the aqueous solution to catalyze the reaction.

The molar ratio of furfuryl ethanol to formaldehyde can be from 3:1 to 0.5:1, optionally 2:1 to 1:1.

The amount of the water-soluble polyvalent metal salt used as the catalyst can be 0.2-0.8% by weight of the amount of furfuryl ethanol.

This reaction can be carried out under air pressure at about 85-105°C, or under pressure and temperature rise. The first problem in carrying out the reaction under elevated pressure and temperature is to avoid boiling the reaction mixture. Thus, for example, if an operating temperature of 140° C. is required, the pressure must be raised accordingly in order to avoid boiling of the reaction mixture.

The content of free formaldehyde or the viscosity state of the product can be set as the end point of the reaction. The final product can be used directly, or diluted with a suitable solvent, including furfuryl alcohol or water.

Although this reaction is described in terms of formaldehyde, other aldehydes of the general formula R-CHO, such as formaldehyde, acetaldehyde, propionaldehyde, furfural, etc., can also be used, where R is a hydrocarbon group containing 1-8 carbon atoms .

General formula I can be used to represent furfuryl alcohol or substituted furfuryl alcohol compounds:

Wherein R ¹ can be an alkyl group, an aryl group, an alkenyl group, an alkanol group, an alkoxy group, an aryloxy group, a halogen or a hydroxyl group. A preferred compound is furfuryl ethanol.

2. Combination of furan resin and resole phenolic resin

The furan resins discussed above may be used in combination with resole resins. Usually, the weight ratio of furan resin to resole phenolic resin is 9:1-1:9.

3. Resole phenolic resin

The resole phenolic resin used in the present invention is a thermosetting resin made by reacting phenol or substituted phenol with formaldehyde or other aldehydes. Preferred substituted phenols may be unsubstituted at two ortho positions, unsubstituted at one ortho and para position, or unsubstituted at two ortho and one para positions. In general, phenols suitable for the preparation of phenolic resins can be used. Phenol and formaldehyde are preferred materials. Some suitable phenolic resins are known as "resoles" and are available in either liquid or solid form.

"Resole phenolic resin" is a resin product in which phenol and an aldehyde are partially condensed according to a certain ratio. Partial agglomeration under this ratio can further condense the product to obtain an infusible state or a hot-melt state. Novolac resin can be used as an ingredient to generate thermosetting phenolic resin by reacting with resole phenolic resin.

Phenol-acetaldehyde resole resins have a molar ratio of phenol to acetaldehyde of 1:1 to 1:3. A preferred way of preparing phenolic resole resins is to mix phenol with an aldehyde, such as formaldehyde, acetaldehyde, furfural, benzaldehyde or paraformaldehyde, under basic catalysis. During this reaction, formaldehyde was used in molar excess. Preferably, the resole phenolic resin has a molar ratio of phenol to formaldehyde of 1:1.2-1:2.5. The resole phenolic resin can be a conventional resole phenolic resin or a modified resole phenolic resin.

The conventional method of preparing conventional resole phenolic resin is, phenol is put into reactor, then adds basic catalyst, such as sodium hydroxide or calcium hydroxide, then, adds aldehyde, such as 50% by weight of formaldehyde aqueous solution, then in Under the condition of increasing temperature, the components are reacted until the desired viscosity or a certain content of free formaldehyde is reached. Finally, the water content is adjusted by distillation.

US Patent No. 5,218,038 discloses a modified resole resin, the entire contents of which are incorporated herein by reference. Reaction of acetaldehyde with a mixture of unsubstituted phenol and at least one phenolic material selected from the group consisting of arylphenols, alkylphenols, alkoxyphenols and aromatic Oxyphenol.

Modified phenolic resole resins include alkoxy-modified phenolic resole resins. Among the alkoxy-modified resole resins, preferred are methoxy-modified phenolic resins. However, the most preferred phenolic resoles are modified ortho-phenylmethyl ether-containing resoles; this material is obtained in the presence of aliphatic hydroxyl compounds containing two or more hydroxyl groups per molecule It is prepared by the reaction of phenol and acetaldehyde. In a preferred method of modification, the above reaction is carried out in the presence of a monohydric alcohol.

The metal ion catalyst used to prepare the modified phenolic resole phenolic resin includes divalent ion salts of manganese, zinc, cadmium, magnesium, cobalt, nickel, iron, lead, calcium, and barium. Also effective catalysts of the present invention are compounds of the general formula Ti( ^OR2 ) ₄ , where ^R2 is an alkyl group containing 3-8 carbon atoms. A preferred catalyst is zinc acetate. These catalysts give phenolic resoles the preference to form bridges to the phenol core, which are ortho-benzyl ether bridges of the general formula _-CH2 ( _OCH2 ) _n , where n is a small positive integer.

4. Trimer of phenol, furfuryl alcohol and formaldehyde

Trimers of phenol, furfuryl alcohol and formaldehyde can be used to replace phenolic or furan resins, respectively.

Trimers of phenol-formaldehyde-furfuryl alcohol can be prepared from the catalytic reaction of phenol, formaldehyde, furfuryl alcohol, wherein the catalyst is a water-soluble polyvalent metal salt, wherein the catalytic reaction is carried out substantially under aqueous conditions. The water soluble salts of common polyvalent metal ions used as catalysts in the present invention provide a significant cost reduction compared to equivalent metal ion soluble organic solvent salts used in the process of US Patent No. 4,255,554 (to Wuskell). In the case of using an acid catalyst, the use of a water-soluble polyvalent metal salt eliminates the need to control the pH of the reaction. However, the polyvalent metal salt catalyzed reaction should be carried out at a pH of less than 7. When uncontaminated phenol, aqueous formaldehyde, furfuryl alcohol, and zinc or lead acetate are mixed in proper proportions, the pH is usually less than 7.

Therefore, the organic solvent does not need to remove water, nor does it need to be subjected to azeotropic distillation. The equipment used is usually related to the type of distillation that needs to be used. In addition, aqueous formaldehyde solutions, such as formalin, can be used to replace paraformaldehyde, which is a solid low molecular weight formaldehyde polymer. Liquid formalin is also easy to control, and the cost is much lower than that of paraformaldehyde.

Water-soluble polyvalent metal salts that can be used to prepare the trimer catalyst include polyvalent ions of manganese, zinc, cadmium, magnesium, cobalt, nickel, tin, copper, iron, lead, and calcium. Preferred catalysts are zinc acetate, lead acetate, or mixtures thereof.

The trimerization reaction is carried out according to the following steps: firstly, furfuryl ethanol is reacted with formaldehyde under the condition of air pressure 85-105°C, and then phenol is added to continue the reaction until the viscosity reaches 100-10,000 centipoise, preferably 200 -5,000 centipoise, the above values are measured values at 25°C.

The maximum reaction temperature is determined by the boiling point of the reaction mixture in the atmosphere. However, the above reaction can be carried out at elevated temperatures up to 140°C in a pressurized reaction vessel, taking care to ensure that the reaction mixture does not boil at elevated temperatures.

The above reaction can also be carried out according to the following steps: first, phenol reacts with formaldehyde, then, furfuryl alcohol is added and the reaction is continued until the viscosity reaches 100-10,000cps, preferably 200-5,000cps, and the above-mentioned value is at 25 Measured value at °C. In addition, under the condition of a water-soluble polyvalent metal salt catalyst, phenol, furfuryl alcohol, and formaldehyde can also be reacted simultaneously to complete the above reaction.

The ratio of unreacted furfuryl ethanol to phenol in the final product depends on the initial ratio of furfuryl ethanol to phenol, the reaction method used and can be determined analytically. The end use of the product will also affect the preferred ratio values.

Distillation is usually required to remove excess water from the reaction product. Excess moisture refers to the amount in excess of that required to dissolve the polyvalent metal salt catalyst. Excess water can appear in the formaldehyde solution or can be generated by coagulation reaction. Removal of excess water can be conveniently accomplished at any point during the reaction that facilitates product processing. An important limitation in removing water content during the reaction is to ensure that there is sufficient water to dissolve a sufficient amount of polyvalent metal salt in the aqueous solution to catalyze the reaction. Therefore, sufficient moisture is required to ensure that all the water-soluble polyvalent metal salt catalysts are dissolved in the aqueous solution.

As mentioned above, the end point of the reaction can be set to reach a product viscosity of 100-1,000 centipoise at 25°C. The obtained phenol-formaldehyde-furfuryl alcohol trimer can be used directly, or diluted with a suitable solvent, including furfuryl alcohol or water.

The ratios of phenol, furfuryl ethanol, and methanol to each other vary widely based on economic considerations and performance requirements. Since furfuryl ethanol is much more expensive than phenol, the cost of the resin can be reduced by using more phenol and less furfuryl ethanol when the performance permits. However, the higher the furfuryl alcohol content in the cured resin, the more resistant the resin will be to some chemicals, especially corrosive solutions. In addition, the higher the amount of furfuryl ethanol that the resin contains when it cures in the final application using an acid catalyst, the more reactive the resin will be.

Generally, the molar ratio of phenol to furfuryl ethanol can range from 0.1:1 to 10:1. The molar ratio of formaldehyde to the sum of phenol and furfuryl ethanol can be in the range of 0.5:1-2:1. Based on the total weight of phenol and furfuryl ethanol, the catalyst dosage ranges from 0.2% to 8%.

Although this reaction is described in terms of formaldehyde, other aldehydes of the general formula R-CHO, such as formaldehyde, acetaldehyde, propionaldehyde, furfural, etc., can also be used, where R is a hydrocarbon group containing 1-8 carbon atoms .

General formula I can be used to represent furfuryl alcohol or substituted furfuryl alcohol compounds:

Wherein ^R3 can be an alkyl group, an aryl group, an alkenyl group, an alkanol group, an alkoxy group, an aryloxy group, a halogen or a hydroxyl group. A preferred compound is furfuryl ethanol.

Furthermore, while phenol is the preferred phenolic reactant, other phenolic substituents can be used, especially those of formula III.

Wherein R ⁴ , R ⁵ , and R ⁶ are respectively selected from hydrogen, hydrocarbon group, oxyalkyl group, hydroxyl group or halogen, and under the substitution conditions, two ortho positions, or one ortho position and one para position, or two ortho positions and one para position are required. Bits are not substituted. In general, phenols suitable for the preparation of phenolic resins can be used. Some examples include o-cresol, m-cresol, p-cresol, octylphenol, nonylphenol, 3,5-dimethoxyphenol, p-tert-butylphenol, p-butoxyphenol, resorcinol Phenol, 3,5-xylenol, 3,5-diethylphenol, catechol, 3,5-dibutylphenol, etc.

After application as a coating, these trimers can be cured with a curing agent (eg, an acid catalyst such as ammonium chloride or ammonium sulfate).

5. Resins containing phenol-acetaldehyde, novolac polymers

In at least one embodiment, the outer coating of at least a single layer of the particles of the invention may contain a curable phenol-acetaldehyde, novolak polymer. The novolac may be any novolak used for proppants. Novolaks can be obtained by reacting phenolic compounds with an aldehyde in the strong acid range. Suitable acid catalysts include strongly acidic mineral acids such as sulfuric acid, phosphoric acid and hydrochloric acid, and organic acid catalysts such as oxalic acid, p-toluenesulfinic acid. An alternative method of preparing novolaks is the reaction of phenol with an aldehyde in the presence of divalent inorganic salts (eg, zinc acetate, zinc borate, manganese salts, cobalt salts, etc.). Different catalysts can be selected to produce different novolaks. For example, zinc acetate is conducive to the ortho-position substitution, and the produced novolaks have different ratios of ortho- to para-aldehyde substitutions on the benzene ring. Novolaks enriched in ortho-substituted positions, ie a high proportion of ortho-substituted novolacs, are more active in deep crosslinking of polymer growth. High proportions of ortho-substituted novolacs are disclosed by Knop and Pilato in "Phenolic Resins" pp. 50-51 (Springer-Verlag), the contents of which are hereby incorporated by reference. A high proportion of ortho-substituted novolaks is defined as a novolak in which 60% of the total ortho- and para-substitutions occur as ortho-substitutions, preferably, 60% of the total ortho- and para-substitutions At least 70% of the ortho substitutions occurred.

Novolac polymers generally contain phenol and aldehyde in a molar ratio of 1:0.85 to 1:0.4. Any suitable aldehyde can be used for this purpose. The aldehyde used may be aqueous formaldehyde, paraformaldehyde, formaldehyde, acetaldehyde, furfural, benzaldehyde, or other aldehydes. Formaldehyde is preferred.

The novolac used in the present invention is usually solid, such as flakes, powders, or other small particles. Novolaks have a molecular weight in the range of about 500-15,000, typically 500-10,000, 1,000-5,000, or 5,000-10,000, depending on the intended use. The novolac molecular weight described in the description of the present invention refers to an average molecular weight.

Typically, the overcoat resin composition contains at least 10% by weight of novolak polymer, preferably at least 20% by weight of novolac polymer, about 50-70% by weight of novolak polymer, or about 85-95% by weight % novolak polymer. Preferably, based on the amount of novolak used, an appropriate amount of hexa(hexamethylenetetramine) in the top or outermost novolak resin layer is chosen such that the resin has a low crosslink density, thereby allowing the material to remain elastic and thus The resin-encased matrix exhibits fracture resistance under cyclic stress conditions and maintains a high degree of adhesion even after prolonged aqueous slurry treatment at elevated temperatures.

The remainder of the coating composition may include crosslinkers, modifiers, or other suitable components.

The phenolic moiety of the novolac is selected from phenols of general formula IV or bisphenols of general formula V, respectively:

R ⁷ and R ⁸ of the general formula IV are respectively selected from alkyl, aryl, aralkyl, or hydrogen. In the general formula V, R ⁹ and R ¹⁰ are preferably selected to be hydroxyl at the meta-position of each aromatic ring. Unless otherwise specified, alkyl is defined as having 1 to 6 carbon atoms, and aryl is defined as having 6 carbon atoms in its ring. In Formula V, X can be a direct link, a sulfonyl group, an unsubstituted alkylene group, or an alkylene group substituted with halogen, cycloalkyl, or halocycloalkyl. Alkylene is a divalent organic group represented by general formula VI:

When X is an alkylene group, R ¹¹ and R ¹² are respectively selected from hydrogen, alkyl, aryl, aralkyl, haloalkyl, haloaryl, halospunalkyl. When X is a haloalkylene, a halogen atom replaces one or more hydrogen atoms of the alkylene portion of the general formula. Preferred halogen atoms may be fluorine or chlorine atoms. Likewise, the halogenated cycloalkyl group preferably has a fluorine atom or a chlorine atom substituting the cycloalkyl part.

A conventional phenol represented by formula IV is phenol.

Conventional bisphenols represented by the general formula V include bisphenol A, bisphenol B, bisphenol C, bisphenol E, bisphenol F, bisphenol S, or bisphenol Z. Other bisphenols suitable as coatings are disclosed in US Patent No. 5,639,806, the entire contents of which are incorporated herein by reference.

Can use the novolac polymer in the present invention, and this novolak polymer contains any phenol represented by general formula IV, the bisphenol represented by general formula V, or one or more phenols represented by general formula IV and general formula V Combinations of one or more bisphenols are represented. The novolak polymers may optionally be further modified by the addition of VINSOL trade name resins (Hercules, Inc, Wilmington, Deleware), epoxy resins, bisphenols, paraffin waxes, or other disclosed resin additives. A kind of method of preparing the phenolic novolak polymer modified by alkylphenol is, according to molar ratio is 0.05: 1 alkylphenol and phenol are mixed; ) under the conditions, the above mixture is reacted with formaldehyde donor. During this reaction, a combination of alkylphenol and phenol was used in molar excess relative to the amount of formaldehyde. Under acidic conditions, the polymerization of methylolated phenols is a faster reaction compared to the initial methylolation of formaldehyde. Thus, a polymeric structure was constructed that included both phenolic and alkylphenolic nuclei linked by methylene bridges and was substantially free of free methylol groups.

In order to prepare a phenolic novolac polymer with one or more phenols represented by the general formula IV, the phenol is first mixed with an acidic catalyst and then heated; then, a 50% by weight formaldehyde solution is added during the temperature rise; Distillation is used to remove the water produced by the above reaction to obtain molten novolac. The molten novolac is cooled and made into flakes.

In order to prepare novolac polymers with bisphenols represented by general formula V, in the process of raising the temperature, bisphenols are mixed with a solvent (for example, n-butyl acetate); then, an acid catalyst (for example, oxalic acid or methanesulfonic acid) and mixed with bisphenol, followed by the addition of an aldehyde, usually formaldehyde; finally, the reaction was refluxed. It should be noted that under conditions of acid catalysis or divalent metal catalysis (eg, zinc, manganese), novolac resins are prepared in which the amount of bisphenol is greater than the equimolar amount corresponding to the aldehyde donor. After reflux, n-butyl acetate was added, and water was extracted by azeotropic distillation. After removal of water and n-butyl acetate, the resin is flaked to obtain a resin product. Furthermore, this polymer can be prepared using water as a solvent.

C. Cross-linking agent and other additives

In practical applications, unless a hardener (curing agent or crosslinking agent) is added, the heated novolac is not only not hard enough, but can still dissolve or melt. Therefore, a cross-linking agent can be used in the curing of novolac resin, thereby overcoming the defect of methylene bridging group and converting the resin into an insoluble and simultaneously infusible state.

However, the amount of curing agent used in the present invention is much lower than that used to make conventional curable proppants or conventional precured proppants. Particularly in conventional proppants containing curable coatings an excess of curing agent is used such that crosslinking or solidification of the resin continues as the temperature increases. Thus, temperature determines the overall rate at which conventional proppants cure. In the present invention, the content of the curing agent is preferably limited so that the resin does not cure beyond a predetermined ratio regardless of the temperature of the resin (ie, novolac). Therefore, this curing agent is a limiting agent. This difference in degree of cure imparts elasticity to the encapsulated proppant of the present invention, which in turn enables the resin-encased matrix to exhibit fracture resistance under cyclic stress conditions, maintaining a high degree of adhesive ability.

Suitable crosslinking agents include hexamethylenetetramine (hexamethylene), paraformaldehyde, oxazolidines, melamine resins, or other aldehyde donors, and/or resole polymers of phenol-acetaldehyde. Each of the above-mentioned crosslinking agents may be used alone or in combination with other crosslinking agents. The resole polymer may contain substituted or unsubstituted phenols, and an amount of crosslinking agent (ie, the amount of acetaldehyde donor).

Typically, the topcoat compositions of the present invention contain up to about 25%, typically 1-5% by weight, of hexamethylenetetramine, based on the total weight of each layer composition in the topcoat, and/or can Up to about 95%, usually less than 70% by weight of novolak polymer. When hexamethylene is used alone as a crosslinking agent, hexamethylene (hexamethylenetetramine) may constitute 1-25% by weight of the particular coating, for example 1-5% by weight. When the phenol-acetaldehyde resole polymer is used alone as the crosslinking agent, the resin of the coating contains about 20-90% by weight of the resole polymer. However, in another embodiment, the resole polymer may comprise 5-50% by weight. The above compositions may also contain combinations of these crosslinking agents.

Typically, hexa(hexamethylenetetramine) is available in the form of an aqueous solution and contains a high water content, eg, 3-20% hexa. Containing a high percentage of water, that is, 80-97%, not only helps the dispersion of the six components, but also controls the reaction. In particular, water acts as a heat sink for absorbing excess heat energy that can inhibit the crosslinking reaction. Correspondingly, the six-component concentration can be adjusted to change the temperature and degree of final curing. For example, if the final temperature needs to be raised for other applications of the coating, the hexaconcentration can be increased (reduced water content), thus limiting the amount of water used to inhibit the reaction from proceeding.

In special cases a variety of different additives can be used corresponding to specific needs. The coating systems of the present invention may include a wide variety of additive materials. The coating may also contain one or more additives, such as coupling agents (e.g., silicones), silicone lubricants, wetting agents, surfactants, dyes, flow modifiers ( For example, flow control agents and flow enhancers), reinforcing agents (eg, fibers), and/or antistatic agents. Surfactants can be anionic, nonionic, cationic, amphoteric, and mixtures thereof. Certain surfactants can also act as flow control agents. Other additives include moisture resistance agents, or heat strength additives. Of course, the additives may be used alone or in combination.

Another potential additive is one or more thermoplastic elastomeric materials applied in at least one coating in or on the surface in sufficient quantity to improve dust removal and/or compressive strength of the granules, in the absence of which elastomeric material, The above problems will appear. US Provisional Patent Application No. 60,462,694, filed April 15, 2003, discloses information regarding the use of thermoplastic elastomers in proppants, the entire contents of which are incorporated herein by reference.

More preferably, an organofunctional silane is used as a coupling agent to improve adhesion at the organic-inorganic interface. These organofunctional silanes are characterized by the following general formula VII:

R ¹³ -Si-(OR ¹⁴ ) ₃ (VII)

Wherein R ¹³ represents an active organic functional group, OR ¹⁴ represents an unstable alkoxy group, such as OCH ₃ or OC ₂ H ₅ . Materials particularly useful for bonding phenolic or furanic resins to silica are amino-functional silanes, an example being given of UnionCarbide Al 100 (gamma-aminopropyltriethoxysilane). Silanes can be premixed with the resin or added separately to the mixer.

In some cases, it is necessary to add a lubricant and agitate after adding the catalyst or six-member and before the product "breaks up" into free-flowing particles. For example, in some embodiments including two inner coatings of furan/resole, the catalyst corresponding to the inner coating of furan/resole may include ammonium chloride solution, which is separately applied after furan/resole is applied. Added after the phenolic coating. Thus, each coating can be allowed to react to a partially cured state. After the addition of the phenolic novolac as the third layer, hexamethylene (hexamethylenetetramine) was added to partially cure the coating.

Preferred lubricants are those that are liquid at the highest temperature and have a sufficiently high boiling point that no loss occurs during agitation. Suitable lubricants include liquid silicones such as Dow Corning Silicone 200, mineral oil, paraffin, petroleum, cocamidopropyl-hydroysultaine (Chembetatine CAS from Chemron Corp, Paso Robles CA, or the synthetic lubricant Acrawax CT, a bis-stearamide of a diamine, available from Glyco Chemicals, Inc, Greenwich, Connecticut). Lubricants may be used in amounts ranging from 0.01% or 0.03% to 0.5% by weight of the particulate material.

The reinforcement may be a variety of materials including natural or synthetic fibers, including glass fibers or other mineral based fibers, or phenolic or other organic based fibers. US Provisional Patent Application No. 60/462,694, filed April 15, 2003, also discloses information on the use of enhancers, the entire contents of which are hereby incorporated by reference.

Thermoplastic elastomeric materials comprise at least one elastic, usually thermoplastic, polymer or copolymer component, usually in an amorphous and/or semi-crystalline state. If the polymer or interpolymer has an amorphous portion, the amorphous portion has a glass transition temperature of less than 50°C, or less than 25°C, or less than 0°C, or less than -25°C. If the polymer or interpolymer has a semi-crystalline fraction, this semi-crystalline fraction preferably has a melting point of 40-80°C, eg 60°C.

An example of a thermoplastic amorphous part that is liquid at room temperature is the HYCAR material.

Preferred semi-crystalline polymers are the ENABLE series of products, which provide particles (pellets) with an equivalent particle size of 0.125-0.25 inches and a melting point in the range of 58-80°C, and are available from ExxonMobil Chemical Company. For example, ENABLE EN 33900 (also known as ENBA) and ENABLE EN 33330 are copolymers of ethylene and n-butyl acrylate in the ENABLE series.

The thermoplastic elastomers are usually based on polymers and interpolymers of unsaturated ethylenically monomeric units selected from at least one group selected from the group consisting of: alkenyl (e.g., vinyl and propenyl), (methyl ) C1-C12 alkyl acrylates, (meth)acrylonitrile, α-olefins, butadiene, isoprene, alkenyl-containing unsaturated siloxanes, anhydrides, and ethers. In the specification of the present invention, the term "(meth)acrylic acid" includes acrylic acid or methacrylic acid, and the term "(meth)acrylonitrile" includes acrylonitrile or methacrylonitrile.

Conventional thermoplastic elastomers include at least one polymer selected from the following substances: C1-C8 alkyl (meth)acrylate polymer; copolymerization of C1-C8 alkyl (meth)acrylate and a monomer The monomer is selected from ethylene, styrene, (meth)acrylonitrile; butadiene homopolymer; butadiene-acrylonitrile interpolymer with functional groups at the end of the chain. Examples of functional groups for butadiene-acrylonitrile interpolymers are carboxyl (COOH), vinyl methacrylate, amine (NH or NH ₂ ), or epoxy. Without being bound by any particular theory, the inventors believe that the functional groups used in the present invention react with the resin molecules.

Preferred thermoplastic elastomers include at least one material selected from the group consisting of polymers of butyl acrylate, copolymers of butyl acrylate and other acrylates, ethylene, ethyl acrylate, or 2-ethylhexyl acrylate. Other preferred thermoplastic elastomers include at least one material selected from the group consisting of carboxy-terminated butadiene-acrylonitrile copolymers, methacrylate vinyl-terminated butadiene-acrylonitrile copolymers, and amino-terminated butadiene-acrylonitrile copolymers. - Acrylonitrile copolymers. The molecular weight of the thermoplastic elastomer can be controlled using chain transfer agents, such as alkyl mercaptans.

The thermoplastic elastomer can be added in liquid form and dispersed into particles; it can also be added in the form of dry granules or pellets.

In the embodiment of particles containing a resin-coated matrix, based on 100 parts of thermosetting resin, the amount of thermoplastic elastomer is in the range of 0.25-50 parts, 0.25-20 parts, usually 0.25-10 parts, or 0.25-5 parts, or 0.5- 2.5 servings. Typically, the pellets contain about 0.005-4.0 wt. %, or about 0.005-2.0 wt. % thermoplastic elastomer, based on total weight, for embodiments using 1-8% resin. Usually, the thermoplastic elastomer is added at the same time as the resin, or after the resin is added for modification, the thermoplastic elastomer is added. For example, the thermoplastic elastomer can be added 0-5 minutes, or 0-3 minutes after the resin is added.

D. Reaction of aldehydes with phenol-acetaldehyde novolacs or bisphenol-acetaldehyde novolacs

It can be modified by reaction with phenol-acetaldehyde novolac or bisphenol-acetaldehyde novolak using an additional amount of acetaldehyde as a basic catalyst. The conventional catalysts used may be sodium hydroxide, potassium hydroxide, barium hydroxide, calcium hydroxide (or lime), ammonium hydroxide and amines.

In the case of phenol-acetaldehyde polymers or bisphenol-acetaldehyde polymers, the molar ratio of added acetaldehyde to phenolic moieties ranges from 0.4:1 to 3:1 based on novolak phenolic moiety monomer units, 0.8:1-2:1 is preferred. Crosslinkable (living) polymers of different chemical structures are thus obtained, generally of higher molecular weight than resole polymers obtained in a single-step process involving the combination of a basic catalyst with The bisphenol monomer and acetaldehyde are mixed, and the molar ratio of the mixed acetaldehyde and bisphenol is the same. Furthermore, it is feasible to use different aldehydes at different stages of the polymerization preparation.

These acetaldehyde-modified polymers can be used in coating compositions for oilfield proppants and foundry sands. These polymers can be used in combination with other polymers (eg, phenol-acetaldehyde novolaks, bisphenol-acetaldehyde novolacs, or combinations thereof) as crosslinkers, or as a component of crosslinkers. When the acetaldehyde-modified polymer is used as a crosslinking agent, it can be used in combination with other conventional crosslinking agents, such as those described above for novolaks.

E. Method for preparing coated particles

A suitable resin (or resins), curing agent, particulate material are mixed under conditions that provide a curable coating composition. Whether the coating composition is of the pre-cured or curable type depends on a number of parameters. These parameters include the resin to hardener ratio, the acidity of the novolak resin, the pH of the resole resin, the amount (and concentration) of the crosslinker, the mixing time of the coating composition and the particles, the composition of the coating during mixing, temperature of the material and particles, the catalyst used in the particle coating process, and other parameters known to those skilled in the art.

Typically, the resin is applied to the surface of the particulate material using a thermal coating process. The thermal coating process includes, using a standard sand heater, first heating the sand to a temperature above the melting point of the resin. This temperature should not be too high, otherwise it will cause damage or thermal degradation of the resin; material). Then, after removing the sand from the heater, place it in the mixer. Because there is no additional heating, the sand must be hot enough when the heater is removed to allow the final coat to be applied. In addition, the temperature of the sand must be low enough that the rate of solidification can be precisely controlled. Once the first resin has completely coated the particulate material (usually 30-60 seconds), the curing agent is added, and the ingredients are mixed for a certain period of time until the particulate material is coated with the curable resin. When a 100% encapsulation rate is required, it can be considered that adding the curing agent after the resin has only encapsulated 99.5% also belongs to the protection scope of the present invention. In one embodiment, the extent of encapsulation can be determined by simple observation. If the liquid resin itself is colored, or contains dyes, by observing the migration of the resin color, the degree of encapsulation of the granular material by the liquid resin can be determined. Typically, agitation is carried out in the presence of a coupling agent, such as an organosilane, and a lubricant, such as silicone oil, such as L-45 produced by DOW Corning Company (Midland, Michigan) (a material of this type is described in U.S. Patent No. 4,439,489 publication, the entire contents of which are hereby incorporated by reference).

For example, the sand is heated to a temperature of about 225-550°F, more conventionally in the range of about 350-550°F, 400-550°F, 400-530°F, 400-450°F, or 400- 410°F, then remove the sand from the heater and put it in the mixer; then, add the first resin to the heated sand at 225°F—the initial temperature of the resin matrix mixture, for example about 225-450° F, 300-410°F, make the resin coat the sand by stirring. Then, add curing agent. Typically, after the first coating is applied, the temperature of the particulate material with the partially cured coating will drop to 300-380°F, or 330-380°F. If additional coats of the first coat are applied, expect a temperature drop of 30-40°F. Multiple coats of the undercoat can be used to smooth or "reduce" the overall irregular shape of the sand or other particulate material. Because the uneven or irregular surface of the particulate material itself can cause problems for sticky proppant packs, multiple coats of curable resins are required.

Once the last coat of the first resin has been applied, the second resin can be applied. Typically, the temperature of the encased particulate material in this step is about 300-320°F. However, this temperature can be adjusted as the amount and concentration of curing agent is varied in order to vary the degree of cure desired. In one embodiment, as described above, the novolak resin is used in flake form, which must be melted in order to coat the coated particulate material.

The temperature during coating depends on the initial temperature of the particles. Since no other heat source is used, the system temperature continues to decrease during the application of each subsequent coat due to process operating conditions, such as melting or evaporating moisture. Preferably, the temperature of the particles is maintained and the following conditions are met: (1) the active mixture cannot be over-converted; (2) enough heat is still maintained to melt the novolak and evaporate water and other volatiles to regain dryness product of. For example, when the pellets are preheated to a temperature of 410°F, the coating process is completed at about 250°F and the wrapped product is discharged.

Usually, in the process of multiple resin coatings, the amount of resin used to coat the particulate material is in the range of about 1-8 wt%, preferably about 2-4 wt%, based on the weight of the particulate material. The incremental amount of resin used to produce each of the inner and outer coatings should be sufficient to form a sufficiently continuous coating that encompasses the entire surface of the particle. In one application, the amount is 10% of the total amount of resin used, and the remaining 90% of the total amount of resin used, as one or several increments, or in any number of additional applications to apply coatings of the same material. Preferably, no one increment should exceed 70% of the total weight of the resin, most preferably, no more than 50% or 30% by weight. In the present invention, the curable resole phenolic resin layer: the curable resole phenolic resin: the ratio of curable novolak does not have a critical value, and the performance of the product is relatively tolerant to the large range of the proportions of each substance in each coating. swing.

Finally, although the coated particles of the present invention have two curable coatings, such as a single inner coating and a single outer coating, it is recognized that providing more than one inner coating and/or outer coating is within the scope of protection of the present invention. scope. The different undercoats are applied by first applying the uncured resin as the undercoat and then applying a catalyst or crosslinker to the resin surface. A second application of uncured resin should only be made after the above resin has cured itself. Because the temperature of the heated particles continues to drop during the application of the first and second coats, each coat temperature that makes up the inner and outer coats produces a different degree of cure. In particular, since the cure rate and amount are directly related to the temperature and amount of crosslinker, the first coat is added at a lower temperature. However, as described above, the same curing rate (or curing speed) can be obtained by adjusting the reaction conditions despite the lower temperature. The resulting coated particles (especially their coating) are resistant to melting at temperatures below 200°F or 225°F.

Embodiments Including Furan/Phenol-Resole-Formaldehyde Coatings and Novolac Coatings

Illustrative of a single figure, proppant 10 comprises matrix particles 20, a first curable coating 30, a second curable furan/phenol-resole-formaldehyde coating 32, and a third curable novolac coating 34 . For each coating, the appropriate resin, crosslinker, and matrix particles 20 are mixed to produce proppant 10. Proppant 10 was prepared such that the total coating weight comprised 1-8% of the total weight of the wrapped proppant. Prior to coating, the particles 20 have a particle size in the range of US Standard Test Mesh Number 8-100.

In a first embodiment of the preparation of the particles shown in the accompanying drawings, the first and second curable inner coatings respectively contain a mixture of furan resin and phenolic resole resin (which can generate trimerization of furfuryl alcohol, formaldehyde and phenol body), and the topcoat contains a curable novolac resin. Reducing the acid catalyst to a moderate level, such as ammonium chloride and ammonium sulfate, can affect the partial curing of the resole phenolic resin; diluting the hexamethylene tetramine to a moderate level can be used to partially cure the novolac resin. By selecting temperature and other process conditions, overcuring of the coating can be avoided. If desired, furan resin (or a trimer of phenol, furfuryl alcohol and formaldehyde) can be used as an inner coating.

A preferred catalyst for furan coating, or a physical or chemical combination coating of furan and resole resin, is ammonium chloride. Another commonly used catalyst is ammonium sulfate. The amount of catalyst used can vary widely depending on the type of catalyst used, the type of resin used, the stirring temperature and the type of agitator. In general, based on the total weight of the resin, the catalyst solids are used in an amount in the range of 0.05-10 wt%, such as 0.2-10 wt% or 0.05-0.25 wt%. Typically, in the two first coats, a 1-5% ammonium chloride aqueous solution is used, with a solid amount of 0.05-0.25% by weight of ammonium chloride based on the total weight of the furan/phenol/formaldehyde trimer. For example, when using a 2.5% aqueous solution of ammonium chloride, 5% by weight of this solution is used, based on the total weight of the trimer. A fully cured resin has an acetone extraction of less than 5% by weight. Most curable resins have acetone extraction greater than 5% by weight.

Preferably, the amount of curing agent used is less than 50% of the total amount required to fully cure the resin, in other words, when the curing agent is exhausted, ie completely consumed, a resin with 5% acetone extraction is produced. More preferably, the amount of curing agent used is less than 25% of the total amount required to fully cure the resin, in other words, when the curing agent is exhausted, i.e. completely consumed, a resin with 5% acetone extraction is produced . Most preferably, the amount of curing agent used is less than 10% of the total amount required to fully cure the resin, in other words, when the curing agent is exhausted, i.e. completely consumed, a resin with 5% acetone extraction is produced .

Hexagram (hexamethylenetetramine) is used for partially curing novolac resin, usually adopts hexagram aqueous solution (4-12%), and the consumption of solid hexagram based on novolac weight is 5% by weight, or based on total coating weight (phenolic novolac Combination of varnish and resole phenolic resin) The amount of the solid six-component is 0.2-1% by weight.

Preheat the granular material to a temperature of 350-550°F, usually 350-450°F, or 400-410°F. In this temperature range, the granular material is resistant to melting. Next, a first additional amount or increment of uncured thermosetting phenolic resole phenolic resin and uncured thermosetting furan resin is added to the preheated particulate material while the particulate material is being agitated, whereby the curable phenolic resin and furan resin Combine individually wrapped pellets. The particulate material is mixed with the first additional amount of resin at up to 550°F, typically 350-450°F or 400-410°F. In particular, the mixing temperature should be high enough to adequately disperse the resin in the particulate material without interfering with the resin's structure and cure limit. Next, the required amount of curing agent is added to the mixture to partially cure the resin. As agitation continues at elevated temperature, the resin partially cures on the surface of the particulate material, producing a free-flowing product consisting of individual particles surrounded by a first inner coating of curable resin. The temperature is gradually decreased from the starting temperature of the particles during the mixing process. Therefore, it is theorized that the temperature after the first coat is about 300-380°F, or usually 330-350°F.

After the first part of the resin has been sufficiently partially cured and the mixture disintegrates into free-flowing particles, the encased particle material is forwardly fed with the second resin and then the second curing agent. Agitation is continued at approximately 250-330°F until the second resin is partially cured and the particulate material again disintegrates into free-flowing particles. Accordingly, a curable second inner coating is applied to the primary coated particulate material under conditions of temperature and catalyst concentration as described above; the second coating is individually wrapped with a curable phenolic resin in combination with a phenolic resin Granules, which can form a transitional encapsulated particle product with a two-layer curable inner coating. The coating steps described above can be repeated, if desired, to apply additional curable undercoats.

Then, to apply the topcoat, the transitional coating particles are mixed with a second curable resin (e.g., novolak resin in molten state) and a suitable curing agent at a temperature of up to about 410°F, usually about 300-400°F. agent mixing; suitable curing agents are exemplified by hexamethylenetetramine, formalin, paraformaldehyde, oxazolidine, phenol-acetaldehyde resole polymers and mixtures thereof. It can be assumed that the particle temperature was close to 300°F when the top coat was completed. The novolac and/or hexa-component is mixed with the transitional coated particle product by melting. Typically, the novolak and/or hexa are supplied as flakes that dissolve quickly at particle temperatures (wrapping with novolac is discussed in more detail below). As agitation continues, the resin forms a curable outer coating on the surface of the particulate material, resulting in a free-flowing product containing individual particles surrounded by partially cured resin. As mentioned above, typically, the sext is supplied as a 4-12% aqueous solution. At any time after the addition of the hexamember and before the mixture "breaks up," it is necessary to add lubricants to the mixture, such as L45 silicone, polydimethoxysiloxane, and Coupling agent, such as Al100 silane.

In order to cure resole resins with low levels of acid catalysts (e.g., ammonium chloride, ammonium sulfate), or to cure novolaks with diluted low levels of hexamethylenetetramine in water, the composition of the reactants, Reaction steps and conditions. Therefore, in this embodiment, it is possible to perform the reaction at a higher temperature and obtain the same degree of curing. For example, if the proppant is heated to a temperature greater than 500°F, such as 530°F, the amount of acid catalyst used to partially cure the furan resin layer (multilayer) can be reduced to 0.01-0.05% based on resin weight; Reduce to 1-2 or 1-4% solution. Therefore, the concentration of hexaions decreases, and the amount of hexaions used (based on the weight of the resin) decreases accordingly.

Although, as stated above, the catalyst should be mixed into the resin corresponding to each inner coat containing the curing catalyst, the curing catalyst may be incorporated into the inner coat resin, or mixed with the inner coat resin, or Add the mixer and coat the proppant surface after adding the resin corresponding to each inner coat. The conventional method is to add the curing agent to the mixer after coating the resin. Useful curing agents should be dissolved in water, or other solvent systems suitable for the catalyst. Before the catalyst is mixed with the resin, be sure to dilute the strong acid catalyst with water to avoid partial reaction between the catalyst and the resin. Solid catalysts which are insoluble at the mixing temperature are preferably used in the form of an aqueous solution. Likewise, the hexa(hexamethylenetetramine) can be added at various points in time, or mixed with the resin of the overcoat. In addition, if provided in the form of an aqueous solution, different amounts of solvent can be used regardless of the concentration of the curing agent to change or control the desired temperature of the final product. For example, when using a conventional 4-12% hexahydric water solution to partially cure the outer novolak resin layer, the temperature of the final product is significantly lower because the encapsulation matrix only retains the heat needed to cure the few additional coats. The relatively dilute six-component solution contains sufficient water, which can effectively inhibit the curing reaction when the temperature drops rapidly. Excess moisture can absorb heat and be evaporated. By adjusting the amount of existing solution, it is possible to further control the rate and degree of curing.

F. Encapsulated Particle Parameters

The following parameters effectively characterize the coated particles of the present invention.

1. Compressive strength

To define the compressive strength of a curable proppant, it is determined according to the following procedure known as the free compressive strength test or UCS test. In this experiment, a 2 wt% KCl solution (dropped with a small amount of detergent to enhance wettability) was added to the proppant. The KCl solution and proppant were stirred gently (approximately 12 pounds of proppant per gallon of KCl) to wet the proppant. Remove entrained gas foam, if present. Use a wetting agent to remove foam, if necessary. The resulting slurry (approximately 100-200 grams, depending on its consistency) was transferred into 2 1.25" OD X 10" stainless steel cylinders equipped with 2 vents at the top and bottom, respectively, to release liquid to reduce air pressure as needed The valve also features a 0-2000psi pressure dial, and a floating piston that transmits pressure to the sample. Usually at least 3 sample modules are used, preferably at least 6 sample modules are used, resulting in product clumps that are longer than twice the diameter. Open the bottom valve during stressing to allow liquid to drain from the slurry, then close the bottom valve during warming. Connect the cylinder to the nitrogen cylinder, apply a pressure of 1000 psi to the cylinder, transfer it to the sample by moving the piston, and then close the top valve, leaving the bottom valve open. With the temperature of the module fluid valve substantially at the experimental temperature, close the bottom valve (closing the fluid valve too quickly when heating the slow, too much liquid is lost from the sample mass through evaporation and boiling).

Preheat the incubator to the set temperature, ie 250±1°F, then move the 2 cylinders containing the samples into the incubator for 24 hours. During curing, stress and temperature are maintained. Stress should be kept within ±10%. During the curing process in the oven, the loose curable proppant particles become solid masses. After 24 hours, remove the cylinder, release the liquid and pressure quickly, and the cylinder compresses the sample into a solid block 1 inch wide and 6 inches long. The sample is cooled, air dried for about 24 hours, and cut (usually sawn) into compressed pieces of length X diameters, at least 2 diameters, preferably 2.5:1. Air dry at less than 49°C (120°F). Typically, the ends of the sample block are smoothed to obtain a flat surface. Sample blocks were cut such that the ratio of length to diameter was greater than 2:1.

The compressed block is placed in a hydraulic press and a force is applied between parallel platens at a rate of approximately 4000 lbs _f./min until the sample block breaks. For specimen blocks with a compressive strength less than 500 psa, use a loading rate of 1000 lbs _f./min . The force required to break the sample block was recorded, and the results of repeated experiments were recorded; using the following formula, the compressive strength of each sample was calculated. Using the average of the two experiments, determine the value for this resin-coated proppant sample:

(Fc, psi)=4×Fg/{[p×d×d][0.88+(0.24d/h)]}

where Fc is the compressive strength (psi)

Fg is the hydraulic meter reading

P is π(3.14)

d is the diameter of the sample block (inch)

h is the diameter of the sample block (inch)

The compressive strength of the sample blocks was determined using a hydraulic press, a Carver hydraulic press (model #3912, Wabash, Indiana).

Typically, the compressive strength of the proppant of the present invention is in the range of 50-3000 psi or higher. However, the reproducibility of UCS experiments is at best about ±10%. Typically, as described below, the single resin coatings of the present invention have a UCS strength greater than 500 psi.

2. Rebinding experiment

Using the sample block (without the slurry test) that has been tested for UCS performance, the recombination experiment is carried out. First, the metal screen (20 mesh) is used to repeatedly rub the sample block into individual particles, and the obtained particles are re-screened to separate Particles in the desired size range (ie, 20/40 mesh), and then the sieved individual particles were again subjected to the UCS test. The UCS value is determined and compared to the initial strength values recorded for these particular resin-coated proppants. The rebinding strength was reported as a percentage of the initial UCS value after rebinding of the sample. Desirably, the percent UCS after recombination is greater than 5% of the initial UCS value, preferably greater than about 10%, usually about 5-10%.

It should be noted that a compressive strength test can be used to indicate whether the coating has cured or is in a curable state. After 24 hours of wet compression at 25°F and 1000 psi, the cured particles were neither bonded nor consolidated, indicating a cured material.

3. Acetone extraction experiment

The acetone extraction test is another way to determine whether a coating is curable. Acetone extraction dissolves the uncured resin fraction. The experiment was carried out as follows: approximately 50 grams of dry resin-coated pellet sample (with known resin coating content) was pre-weighed, then placed in a Soxhlet thimble, and the sample was refluxed with acetone for 2 hours . After the treated samples were dried, the rate of change in resin content was recorded as the acetone extraction rate. Especially, because uncured resin is soluble in acetone, and cured resin is insoluble in acetone. Therefore, acetone reflux will only extract the uncured portion of the sample. By weighing the sample before and after the acetone reflux treatment, the percent weight change can be determined to calculate the degree of cure.

For example, conventional cured resins typically have a weight change of less than 0.2 grams (corresponding to a 50 gram test sample), corresponding to an acetone extraction of less than 5%. In contrast, the uncured resins used in the present invention typically exhibit a weight change of greater than 2.0 grams. Therefore, the proppant used in the present invention with multiple layers of resin as a whole (or a single layer if required) exhibits an acetone extraction rate greater than 15%, such as 15-50%, or 15-30%, 15-40%, while " "Pre-cured" resins typically have an acetone extraction of less than 5%. When each of the resin coatings used in the present invention was in a curable state, the acetone extraction rate was determined after addition of the curing agent and before any other resin was applied to the partially cured resin surface.

4. Sticky point temperature experiment

The tack point temperature is another indicator of whether a coating is curable. The experiment was performed as follows: The wrapped material was placed in a heated melting point rod to determine the minimum temperature at which the wrapped material became tacky. A "stick temperature" greater than 350°F at the hottest end of the rod usually indicates cured material and depends on the resin system used. The melting point rod is a brass rod (18 inches long and 2 inches wide) with an electric heating element on one end. Thus, along the length of the rod, a temperature gradient can be created and the temperature of the rod can be measured using temperature probes or thermocouples. Using a funnel, place a uniform amount of resin-coated particles (such as sand) onto the heating rod and let it cure for 60 seconds. Then, tilt the rod so that the uncured proppant falls down. The melting point is the lowest temperature at which the resin-coated particles become connected blocks; even if the rod is tilted to 90 degrees, the resin connected into the blocks will not fall off the rod. Typically, the cured coating has a tack point temperature in the range of 200-300°F, for example 200-250°F.

5. Pulverization rate experiment

The crush rate test can determine the strength of the proppant pack. Select the 20/40 purpose sieving range to wrap the granular material, and weigh it. The samples were then pressed at 10,000 psi for 3 minutes in the comminution unit. Next, the pressure is removed and the sample is poured onto the same 20/40 mesh screen. The portion passing through the 40 mesh screen was weighed and compared to the first weight. The pulverization rate is equal to the ratio of the weight of the permeated part to the total weight of the sample before pressing. The encapsulated particles of the present invention typically exhibit 2-10% comminution. This process is disclosed in US Department of Petroleum Recommendation #56, the entire contents of which are hereby incorporated by reference.

In this experiment, unwrapped or wrapped granular materials with a sieve range of 20/40 mesh were selected and weighed. In particular, use a sample divider to obtain 80-100 grams of sample before screening. A 40-gram sample was screened and placed into a test cell (1.5-3 inches in diameter, Rockwell C hardness of 43 or higher (Rockwell C 60 preferred); using a hydraulic loading system (hydraulic press), 5000 lbf, Forney, Inc , Model No.FT-0040D or equivalent). The samples were then pressed at 10,000 psi for 3 minutes in the comminution unit (pressurized for one minute and held for an additional two minutes). Next, the pressure is removed and the sample is poured onto the same 20/40 mesh screen. The portion of the crushed fines that passed through the 40 mesh sieve was weighed and compared to the first weight. The pulverization rate is equal to the ratio of the weight of the pulverized fine particle fraction to the total weight of the sample before pressing.

6. Cyclic stress test

Cyclic stress testing can determine how a consolidated proppant pack responds to stresses and movements induced by the formation during normal operation. Consolidated proppant samples were used at a loading of 3-4 lb proppant per square foot of fracture. 30 cycles were performed where during each cycle a first pressure of 1000 psi was applied to the consolidated proppant through the plunger within the selected pressure cell temperature range 150-350°F, typically 195°F Fill up and hold for a certain time, then, within the above temperature range, apply a first pressure of 4000psi to the consolidated proppant sample through the plunger and hold for a certain time; thus, a cycle is defined by time, which includes 1000psi The time taken down, and the time taken at 4000 psi, and the time taken back to 1000 psi again, totaled 90 minutes. After this cycle, the pressure was reduced and returned to the original 1000 psi, and a new cycle was started. The amount of proppant return per cycle can be determined by the mass of proppant recovered in the experimental unit. Because of the continuous flow of water through the test cell during circulation, any proppant that falls from the proppant pack can be recovered from the test cell. After 30 cycles, the reflux rate can be measured by summing the proppant reflux and comparing this value with the total mass initially entering the experimental unit (as a percentage of the initial value). The coated particles of the present invention have a reflux rate of less than 15%, preferably less than 10%, or less than 5% when this test is conducted at 195°F. The experimental unit was an 8 inch square unit with a sandstone unit liner and had a test load of 4 psi, equivalent to having 100 grams of proppant in the test unit. The turbulent flow through the experimental cell during circulation was 17 cm2/min of 2% KCl solution.

G. Use of encapsulated particles as proppants

The coated particles of the present invention can be used as a single proppant in a 100% proppant pack, or as a partial replacement for existing commercially available ceramic- or sand-based proppants, resin-coated and/or uncoated proppants, or Mixtures of the two, such as coated particles, may comprise 10-50% by weight of the proppant in the injection well. For example, a curable proppant of the present invention can be placed at the fracture opening in the well after precured proppant or unwrapped proppant has been placed in the well.

The method includes exposing the resin composition to sufficient heat and pressure in the formation to cure the curable resin, thereby causing crosslinking of the resin and consolidating the curable proppant of the present invention. In some cases, an activator is used to promote consolidation of the curable proppant. In another embodiment of using the curable resin composition on the surface of the proppant, the method further includes catalyzing the curing reaction with a low temperature acid at a temperature as low as 70°F. Examples of low temperature acid catalyzed curing reactions are disclosed in US Patent No. 4,785,884, the entire contents of which are incorporated herein by reference.

After using unpacked proppant, or pre-cured proppant, or another curable proppant in the portion of the wellbore closest to the fracture, whether the coated particles are used alone as a proppant or together with other proppants at the end Both, the coated particles of the present invention have considerable advantages.

H. Use of Encased Particles as a Gravel Pack for Sand Control

It is well known that the wellbore of an oil or gas well is supported by a gravel pack. Another aspect of the invention is that the encapsulated particles of the invention may be used as a gravel pack. The encapsulated particles of the present invention may be provided in published standard sizes as gravel packs. Gravel packing is usually carried out in multiple layers. The strength requirements for proppant particles are generally higher than for gravel packs. Gravel packing can be used for sand control to stop the flow of fine sand in the formation from flowing into the wellbore.

For example, a gravel pack can be generated adjacent to the wellbore to form a permeable solid barrier that restricts the flow of spun yarn by the following steps:

a. Injecting encapsulated particles into the sand in the area surrounding the wellbore;

b. curing the injected particles in this area;

c. Create a permeable solid barrier that can restrict the flow of the spun yarn.

For example, a cylindrical structure is filled with resin-containing particulate material (eg, proppant) and injected into the wellbore. Once in place, the improved performance of the product of the present invention is beneficial as the proppant solidifies to act as a filter or screen, thereby eliminating backflow of sand, other proppants, or formation particles. This great advantage is that it eliminates the possibility of backflow of various particles into the surface equipment.

VI. Embodiment

The following examples illustrate the invention; unless otherwise indicated, all parts and percentages are by weight; all mesh sizes are US Standard mesh sizes.

Example 1-5

A curable proppant with a multi-layer inner coat of resole-furan resin and a single outer coat was prepared following the general coating process described below. Heat 1000 grams of substrate to be coated to 400-410°F with agitation in a Hobart C-100 laboratory mixer, then turn off heat. Add one or more resins, as well as catalysts, curing agents, or other additives as desired, as indicated below (in chronological order). At the end of this cycle, the material was released from the mixer as a free-flowing product containing individual grains of sand encapsulated by a curable resin, which was rapidly cooled and qualified. Determine the sticky melting temperature of this product.

Table 1A shows the steps and ingredients for encapsulating the bauxite, in which the bauxite was heated to the desired temperature in a mixer, and then the ingredients were added in the ratios and times indicated. Amounts in Table 1A are in grams unless otherwise stated. The measured results are shown in Table 1B and Table 1C.

In the examples of Table 1A and Tables 2A and 3A, the silane was Al 100 adhesion promoter supplied by Union Carbide Corporation. Proppants can be coated with: PFFA resole known as Plasti Flake EX18663, phenol-formaldehyde, resole, furfuryl alcohol terpolymer supplied by Borden Corporation (North American Resins, Louisville, Kentucky) .

Furthermore, the proppant may also be coated with PF novolak 5150 known as Plasti Flake EX5150, a phenol-formaldehyde novolak supplied by Borden Corporation (North American Resins, Louisville, Kentucky).

Chembetaine is an abbreviation for the name of a lubricant. It is a fatty acid amine derivative (coamidopropyl hydroxysultaine) purchased from Chemron. Table 1A Ingredient Weight (grams) time (seconds) Control Experiment A _{1, 2} Experiment 1 _{1, 2} Experiment 2 _{1, 2} Experiment 3 _{1, 2} Experiment 4 _{1, 2} Experiment 5 _{1, 2} 20/40 Bauxite 0 1000 1000 1000 1000 1000 1000 Initial temperature (°F) 0 460 410 460 410 460 410 PFFA Resole Ex18663 0 twenty two twenty two twenty two twenty two twenty two twenty two Al100 silane 7 0.4 0.8 0.8 0.4 0.4 0.4 The amount of ammonium chloride % concentration used 40 10%/1.16 10%/1.16 10%/1.16 10%/1.16 10%/1.16 10%/1.16 PFFA Resole Ex18663 80 twenty two twenty two twenty two twenty two twenty two twenty two The amount of ammonium chloride % concentration used 120 10%/2.32 10%/2.32 10%/2.32 10%/2.32 10%/2.32 10%/2.32 PF Novolac Ex5150 160 15 16 ² 16 ² 15 15 15 Hexamethylenetetramine 200 40%/ 40%/ 4%/ 12%/ 4%/ 4%/ (Six yuan)% concentration 5.6 5.6 5.6 5.6 5.6 5.6 Chembetaine 240 0.3 0.3 0.3 0.3 0.3 0.3 Unload and cool 280 ₁ @ 3.6-4.2% LOI ₂ @ containing line 7% Kynol novoloid fiber from Kynol Corporation of America, Pleasantville, NY Table 1B properties after cooling Control Experiment A Experiment 1 Experiment 2 Experiment 3 Experiment 4 Experiment 5 Sticky Point (°F) >360 323 243 251 266 246 Crushing rate @10000psi 0.1 0.1 0.1 0.4 0.13 0.2 Acetone extraction rate ₃ 0 14 twenty four 41 19 43 ₃ The acetone extraction rate can be used to identify the "curability" or degree of cross-linking retained by the coated particles, and can clearly identify the curability of the formed coating. Table 1C nature Control Experiment A Experiment 1 Experiment 2 Experiment 3 Experiment 4 Experiment 5 UCS250°F/24 hours ₄ 225 882 342 1100 815 950 UCS @ 1 hour, slurry 200°F ? 802 336 1005 874 987 UCS @ 2 hours, slurry 200°F ? 958 222 858 884 830 UCS @ 3 hours, slurry 200°F ? 530 ? 1000 838 925 %UCS after rebinding experiment ₅ ? ? ? 2% 11% 30 cycles ₆ reflux rates 9% <1% >15% 1% 2% <1% ₄ UCS experiments described in the section entitled Encapsulated Particle Parameters ₅ Rebinding experiments described in the section entitled Encapsulated Particle Parameters ₆ Cyclic stress experiments described in the section entitled Encapsulated Particle Parameters

Processing the substrate and coating components at this temperature (with ratios and reaction times between the components as directed) yields ferrovana in multiple coatings, each of which is not highly cross-linked. The effect obtained is an elastic coating that in turn renders the resin-coated substrate resistant to fracture under cyclic stress conditions and retains a high degree of adhesion even after prolonged aqueous slurry treatment at elevated temperatures.

These experimental results demonstrate the performance of the coated particles of the present invention, which can withstand at least 30 stress cycles without breaking the bonded matrix. These experimental results also demonstrate that the resin-coated material has a reflow rate of less than 1% after these cyclic stresses (bottom row of Table C).

Table 1C demonstrates that the material obtained after discharge can be slurried in aqueous KCl at 200°F and its bond strength can be determined using a free compressive strength test. Compression blocks were prepared at 250°F and 1000 psi pressure, then the compressive strength in the slurry was determined as a function of time, which maintained the potential for near full bond strength (within experimental error). After each sample has been tested for UCS performance, the compressed block is disassembled and sieved into individual particles before the UCS test is performed. These materials were found to retain the ability to reform into compact blocks, reflecting the ability of the consolidated material to recombine in the formation if it fractures during use.

sand example

The following examples demonstrate the invention and document various properties of resin-coated sand. In these examples, the sand was heated in a mixer to the desired temperature and then the ingredients were added in the ratios and times shown in Tables 2A and 3A. Tables 2B and 2C and 3A, 3B, 3C show the experimental data obtained. Amounts used in Tables 2A and 3A are in grams unless otherwise stated.

Tables 2A and 3A show examples where the substrate was 20/40 white sand. These examples illustrate that catalysts and curing agents can produce the same level of cure in the coating at reduced temperatures. This view is supported by evidence for softening point (top layer dominates) and acetone extraction rate (where all coatings contribute). Examples 17 and 19 illustrate that the acetone extraction is actually greater than the weight of a single top layer (overcoat) (approximately 30%). This indicates that the inner coating is in a state where it can be cured. Table 2A Ingredient _{7, 8} weight (g) time (seconds) Control Experiment B Experiment 6 Experiment 7 Experiment 8 Experiment 9 Experiment 10 Experiment 11 20/40 sand 0 1000 1000 1000 1000 1000 1000 1000 Initial temperature (°F) 0 460 460 460 460 460 410 460 PFFA Resole Ex18663 0 twenty two twenty two twenty two twenty two twenty two twenty two twenty two Al100 silane 7 0.4 0.4 0.4 0.4 0.4 0.8 0.4 The amount of ammonium chloride % concentration used 40 10%/1.16 10%/1.16 10%/1.16 1%/1.16 1%/1.16 10%/1.16 PFFA Resole Ex18663 80 twenty two twenty two twenty two twenty two twenty two twenty two twenty two The amount of ammonium chloride % concentration used 120 10%/2.32 10%/2.32 10%/2.32 1%/2.33 1%/2.33 2.5%/1.16 10%/2.33 PF Novolac Ex5150 160 15 15 15 15 15 16* 15 Hexamethylenetetramine (hexa)% concentration 200 40%/5.6 4%/5.6 10%/22.4 40%/5.6 40%/5.6 4%/5.6 4%/5.6 Chembetaine 240 0.3 0.3 0.3 0.3 0.3 0.3 0.3 Unload and cool 280 ₇ @3.6-4.2% LOI ₈ @ Contains 7% Kynol novoloid fiber from Kynol Corporation, Pleasantville, NY Table 2B properties after cooling Control Experiment A Experiment 6 Experiment 7 Experiment 8 Experiment 9 Experiment 10 Experiment 11 sticky point >335 243 265 >335 >335 296 239 (°F) Crushing rate @10000psi 3.1 3.3 3.7 2.9 4.4 5.1 3.2 Acetone extraction rate ₇ 1 18.8 18.4 2.9 8.6 18 24.3 ₇ The acetone extraction rate can be used to identify the "curability" or degree of cross-linking retained by the coated particles, and can clearly identify the curability of the formed coating. Table 2C performance Control Experiment A Experiment 6 Experiment 7 Experiment 8 Experiment 9 Experiment 10 Experiment 11 UCS 250°F 24 hours 250 365 353 146 283 943 330 Table 3A ingredients ₁₀ time seconds Experiment 12 Experiment 13 Experiment 14 Experiment 15 Experiment 16 Experiment 17 Experiment 18 Experiment 19 20/40 sand 0 1000 1000 1000 1000 1000 1000 1000 1000 Initial temperature (°F) 460 460 460 460 460 410 460 400 PFFA Resole Ex18663 0 twenty two twenty two twenty two twenty two twenty two twenty two twenty two twenty two Al100 silane 7 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 The amount of ammonium chloride % concentration used 40 1%/1.16 3/1.16 3%/1.16 3%/1.16 2.5%/1.16 2.5%/1.16 2.5%/1.16 2.5%/1.16 PFFA Resole Ex18663 80 twenty two twenty two twenty two twenty two twenty two twenty two twenty two twenty two The amount of ammonium chloride % concentration used 120 1%/2.33 3%/2.33 3%/2.33 3%/2.33 2.5%/1.16 2.5%/1.16 2.5%/1.16 2.5%/2.33 PF Novolac Ex5150 160 15 15 15 15 15 15 16* 15 Hexamethylenetetramine (hexa)% concentration 200 4%/5.6 40%/5.6 12%/5.6 12%/5.6 12%/5.6 12%/5.6 4%/5.6 4%/5.6 Chembetaine 240 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 Unload and cool 280 280 280 280 280 280 280 280 280 ₁₀ @3.6-4.2%LOI Table 3B properties after cooling Experiment 12 Experiment 13 Experiment 14 Experiment 15 Experiment 16 Experiment 17 Experiment 18 Experiment 19 sticky point 257 >335 305 283 304 250 254 247 (°F) Crushing rate @10000psi 5.6 3.5 4.7 4.1 5.6 9.3 5 7 Acetone extraction rate ₇ 10.8 4.7 5.6 7.7 28 44 25 38 ₁₁ The acetone extraction rate can be used to identify the "curability" or degree of cross-linking retained by the encapsulated particles, and can clearly identify the curability of the formed coating. Table 3C performance Experiment 12 Experiment 13 Experiment 14 Experiment 15 Experiment 16 Experiment 17 Experiment 18 Experiment 19 UCS 250°F 24 hours 445 263 438 350 267 567 327 1003

As noted above, the coated particulate material of the present invention retains a high degree of compressive strength whether or not subjected to slurry circulation, as determined by the UCS method described above.

As noted above, the proppants of the present invention include multiple coatings of a curable resin on the substrate surface. Although multiple layers of resin are applied in an uncured state, for each layer of resin the resin is partially cured upon addition of a corresponding curing agent, but it is preferred that the resin remains in a curable state in the final product. That is, each resin coating remains in a curable state despite the addition of multiple coatings (and the partial curing of the additional coatings). As evidence of this, the coated particles of Example 19 were prepared according to the procedure of Table 3A, however, if necessary, the above procedure was modified and as follows:

Experiment #1: Stop step 40 seconds after first addition of ammonium chloride. Then, each of the remaining ingredients was replaced with water. After 280 seconds, the particles containing the monocoat were released.

Experiment #2: Stop the procedure after the second addition of ammonium chloride. Then, the remaining ingredients were replaced with water. After 280 seconds, the particles containing the double coating were released.

Experiment #3: The entire procedure of Table 3A was performed. After 280 seconds, the particles containing the three coats were released.

Experiment #4: Combining two additions of FFFA resole into one addition at "0" time point followed by two doses of ammonium chloride over 40 seconds. After 160 seconds, the remaining steps are performed.

Table 3D shows the acetone extraction rate of each experimental particle. Table 3D experiment number Acetone extraction rate% 1 41 2 52 3 48 4 47

It can be seen from Table 3D that each curable coating is still in a curable state after being covered with other resins and partially cured.

Table 4 illustrates the changes in the compressive strength of the samples of the present invention and the samples of the comparative example. Table 4 sample Reaction conditions Initial USCpsi UCS @ 1 hour slurry psi UCS retention rate % UCS @ 2hr Serum psi UCS retention rate % UCS @ 3 hr slurry psi UCS retention rate % Comparative experiment B Fully Curable Layer 1 2820 2000 71 1466 56 - - Comparative experiment C 1 layer can be cured 705 535 76 466 66 330 47 Comparative experiment D cured/curable 530 161 30 Experiment 1b 100% Acid/30% Hex @ 410°F 883 802 91 958 99 530 60 Experiment 2a 100% Acid/30% Hex @ 460°F 345 350 102 365 107 Experiment 2b " 343 336 98 222 65 Experiment 3a 25% Acid/30% Hex @ 400°F 1170 1005 86 858 73 Experiment 3b " 1100 1000 91 858 78 1000 91 Experiment 3c " 730 572 78 experiment 3d " 635 638 100 Experiment 3e " 900 915 102 Experiment 4a 25% Acid/10% Hex @ 460°F 800 874 107 653 80 Experiment 5a 25% Acid/10% Hex @ 400°F 1450 987 68 830 57 Experiment 5d " 558 600 108 Experiment 5b " 877 817 93

As shown in Table 4, "a" at the end of each example indicates that sand is used as particles for the first time, "b" indicates that bauxite is used for the first time, "c" indicates that sand is used for the second time, and "d" indicates mild Weight of ceramic particles, "e" indicates the first use of bauxite. The proppant has two inner coats of curable resole resin and a single outer coat of curable novolak resin.

In Table 4, the acid catalyst is ammonium chloride; "% acid" represents the ratio of the amount of catalyst used to obtain the "pre-cured state" at this temperature to the amount of fully cured resin; The part of the curing agent used in the "completely cured state", the so-called "completely cured state" can be in the coating process or in the subsequent formation fractures; the temperature represents the initial temperature of the matrix. For example, "25% sexamate" means that the amount of sexamate used is 25% of the amount used to prepare the pretreated catalyst.

Control Experiment B, a single coating of curable novolac resin encasing sand particles, exhibited nearly 100% acetone extraction.

Control C is a single coating of curable novolac resin similar to Control B, but is partially cured and still curable, i.e. has about 30% acetone extraction and can be adequately cured downhole with sufficient hexa . In contrast to the preferred formulation used to prepare the encapsulated particles of the present invention, during the preparation of Control Experiment C, sufficient curing agent was used to fully cure the single resin layer.

Control Experiment D has a cured novolac first or inner coat that is fully cured by the six-component, and a novolac second or outer coat that is in a curable state that can be used downhole under six-component sufficient conditions. Fully cured. The above two coatings enclose the sand particles. In order to determine the UCS value, two 6-inch blocks of material were made, and each block of material was divided into two to generate 4 samples to be tested. The data reported in Table 4 reflect the mathematical average of 4 experimental samples.

As can be seen from Table 4, after 3 hours of slurry treatment, the coated granular material of the present invention exhibits a% UCS retention, at least 60%, usually greater than 80%, preferably greater than 90%, most preferably is close to 100%. Furthermore, it can be seen that the coated particulate material of the present invention exhibits an absolute strength of at least 500 psi, typically greater than 600 psi, preferably greater than 850 psi, and most preferably greater than 1000 psi after 3 hours of slurry treatment.

Example 20 - Ability to withstand storage at 140°F

Table 5 shows comparative data of the melting point (tack point) and free compressive strength retention values of the curable "proppant AA" according to Example 1 of the present invention and the control proppant. Prepared as described above, which includes a multi-layer resole-furan resin inner coating and a single outer coating, the control proppant contains a multi-layer curable phenolic resin inner coating and a 140 ° F environment (placement in an incubator) for the cured topcoat. In order to carry out the sticky point test and UCS determination, 10,000 grams of each sample was put into a thermostat during the test period and samples were taken periodically. All proppants were placed in individual metal gallon containers, each holding 5,000 grams of material.

Proppant AA has an approximately 100% pure, alumina matrix with a specific gravity of 3.4-3.6 and 3 curable coats. The first coating (innermost coating) is composed of FA resole phenolic resin, which is a trimer of phenol, formaldehyde and furfuryl alcohol with ammonium chloride catalyst. The second coating (intermediate coating) is composed of FA resole phenolic resin, which is a trimer of phenol, formaldehyde and furfuryl alcohol with an ammonium chloride catalyst. The third coat (outermost coat) contains at least partially curable novolak resin and HEXA. Proppant AA can be prepared according to Example 1. table 5 storage days Proppant sample Melting (sticky) point (°F) UCS@250°F 0 20/40 proppant AA20/40 control proppant 277275 873498 8 20/40 proppant AA20/40 control proppant 277302 845325 14 20/40 proppant AA20/40 control proppant 285309 835318 28 20/40 proppant AA20/40 control proppant 279315 1013160

The UCS values in Table 5 illustrate that the proppants of the present invention have higher UCS retention values than the control proppants after long-term storage at 140°F. The significance of the unchanged stick point temperature of proppant AA is reflected in the UCS value. That is, the proppants of the present invention retained curability and binding ability compared to the control proppants.

Obviously, other specific implementations that are different from those described above also belong to the conception and scope of protection of the present invention. Accordingly, the invention is not limited by the foregoing description, but is only limited by the appended claims.

Claims (86)

1 A coated particles, which contains:

Grained matrix;

Fully wrapped in a single layer on a substrate at least a first set of a curable resin;

Fully wrapped in at least a first set of single-curable resin layer on at least a second Curable resin cap.

2, the coated particles according to claim 1, wherein the coated particles have more than 15% acetone Extraction rate.

3, the coated particles according to claim 1, wherein the first material and the ratio of the coated particles To 12 pounds per gallon of KCl solution 2% KCl aqueous solution of the particles to form a mixture, Then, the mixture was heated at 200 ° F for 3 hours finally determined experimentally in accordance with the UCS The coated particles have a compressive strength greater than 60 percent retention.

4, the coated particles according to claim 1, wherein the 140 ° F for 28 days in accordance with the stored UCS experimental determination of the resulting coated particles have more than 80% of the compressive strength retention rate.

5, the coated particles according to claim 1, wherein the 195 ° F, the maximum pressure of 4000psi, Minimum pressure 1000psi conditions for 30 cycles of cyclic stress test, the packet Leggings particles have a rate of less than 15% of the reflux.

6, the coated particles according to claim 1, wherein the coated particles having at least 50psi pressure Strength of rebound strength.

7, the coated particles according to claim 1, wherein the coated particles having a first pressure strength UCS Of at least 5%, and compressive strength of at least 50psi rebound strength.

8, the coated particles according to claim 1, wherein the coated particles having a first pressure strength UCS Rebound of at least 10% of the strength.

9, the coated particles according to claim 1, wherein the phenol resin is selected from the first set - acetaldehyde, ring Epoxy resin, urea - aldehyde, furfuryl alcohol, melamine - aldehyde, polyester, alkyd Fat, novolac, furan resin, phenol resin and furan resin, and a combination of benzene Phenol, furfuryl alcohol and an aldehyde trimer;

Second resin is selected from phenol - aldehyde, epoxy resin, urea - aldehyde, furfuryl alcohol, Melamine - aldehyde, polyester, alkyd resin, novolac, furan resin, phenolic resin Fat and furan resin, and a combination of phenol, furfuryl alcohol and an aldehyde trimer; wherein The first set of the resin composition and the second resin composition may be the same or different.

10, the coated particles according to claim 1, wherein the first set of the curable resin is selected from furan Resin, a phenolic resin and furan resin, and a combination of phenol, furfuryl alcohol and an aldehyde Trimer; second curable resin is a novolak resin curable.

11, the coated particles according to claim 10, wherein the phenolic resin portion including those containing phenol Or a substituted phenol, a thermosetting resin, formaldehyde, or other aldehydes, wherein the substituted phenol Can be two ortho, one ortho or para position to one, or the two ortho and One pair of bits have not been replaced.

12, the coated particles according to claim 10, wherein the phenolic resin portion comprises a phenol Aldehyde.

13, the coated particles according to claim 10, wherein the first curable resin include phenol, Furfuryl alcohol and an aldehyde trimer, wherein said aldehyde is formaldehyde.

14, the coated particles according to claim 10, wherein said part is a resol phenol resin Phenolic resins.

15, the coated particles according to claim 14, wherein the furan resin is furfuryl alcohol moiety is selected from Reaction products with formaldehyde, furfuryl alcohol self-dimer, furfuryl group and a reaction product of formaldehyde, Furfuryl self copolymers, and mixtures thereof.

16, the coated particles according to claim 1, the sticking point of the range of experimental determination of the melting point 200-300 ° F.

17, the coated particles according to claim 1, wherein each layer is less than the amount of curing agent used in the tree Fat 50% of the amount of fully cured.

18, according to the coated particles according to claim 1, wherein each layer of curing agent used is preferably Is less than the amount of the resin is fully cured 25%.

19 A method according to claim 1, wherein the granules, which comprises the steps of: First particle matrix preheated to 225-550 ° F; then mixed with the first curable resin, The substrate surface to form a first curable resin coating; Subsequently, containing a second curable then At least a monolayer coating of resin wrapped first curable coating.

20, The method of claim 19, wherein the first curable resin is selected from furan resins, Furan resin, phenolic resin and a combination of phenol and furfuryl alcohol and formaldehyde trimer, Wherein the second curable resin is a curable phenol-formaldehyde novolak resins.

21, The method of claim 20, wherein the particles with the matrix resin mixture selected from the first Substances in contact with a catalyst:

(1) pKa of the acid is less than or equal to 4;

(2) Water-soluble salts of polyvalent metal ions;

(3) pKa less than or equal to 4 ammonium or amine salt of the acid.

22, The method of claim 21, wherein (1) in an acid selected from phosphoric acid, sulfuric acid, nitric Acid, benzenesulfonic acid, toluenesulfonic acid, xylene sulfonic acid, sulfamic acid, oxalic acid and salicylic acid.

23, The method of claim 21, wherein (2) of the salt is selected from sulfates and chlorides.

24, The method of claim 21, wherein (2) of the metal salt is selected from Zn, Pb, Mn, Mg, Cd, Ca, Cu, Sn, Al, Fe, and Co.

25, The method of claim 24, wherein the catalyst section (3) in the salt is selected from nitrate, Chloride, sulfate, fluoride.

26, The method of claim 21, wherein the catalyst is selected from acidic pKa of less than or equal to 4 Ammonium salts.

27, according to the method claimed in claim 26, wherein the particles prepared, wherein the catalyst is chloride Ammonium.

28, The method of claim 19, wherein the substrate is selected from particles of sand, bauxite, zircon, ceramic Ceramic particles, glass beads, and mixtures thereof.

29, The method of claim 19, wherein the substrate is a particle diameter of 8-100 mesh Sand.

30, The method of claim 19, further comprising the steps of:

To the first curable resin coating on the added amount of partially cured up to a first Curing agent;

The second curable resin coating on the added amount of a second up to a partially cured Curing agent.

31, a treatment method for the formation, including the following steps of: applying the right formation Claim 1, wherein said coated particles and a mixture of hydraulic fracturing fluids, and in the formation fracture Inside the particles solidify.

32 A method of filling gravel to form the wellbore, which includes the package of claim 1 Wrapped particles into the wellbore.

33 A coated particles, including: particulate substrate and coating the surface of the resin-coated Layer, in which 140 ° F for 28 days and stored in accordance with the parcel UCS test pieces obtained were measured Tablets having a compressive strength of at least 80% retention.

34 A coated particles, including: particulate substrate and coating the surface of the resin-coated Layer, wherein the first material and the ratio of coated particles KCl solution 12 pounds per gallon of particles 2% KCl solution to form a mixture, then the mixture was heated at 200 ° F for 3 , The final UCS experimentally determined according to the obtained coated particles have more than 60% of the pressure Strength retention.

35, the coated particles according to claim 34, wherein the coated particles have more than 90% of the material Compressive strength retention.

36, The method of claim 36, wherein the first material and the ratio of coated particles per gallon 12 pounds of particles KCl solution 2% KCl solution to form a mixture, followed by the mixture Was heated at 200 ° F for 3 hours finally obtained was measured in accordance with the parcel UCS test pieces Grains with compressive strength greater than 500psi.

36, The method of claim 36, wherein the first material and the ratio of coated particles per gallon 12 pounds of particles KCl solution 2% KCl solution to form a mixture, followed by the mixture Was heated at 200 ° F for 3 hours finally obtained was measured in accordance with the parcel UCS test pieces Grains with compressive strength greater than 500psi....

36, The method of claim 36, wherein the first material and the ratio of coated particles per gallon 12 pounds of particles KCl solution 2% KCl solution to form a mixture, followed by the mixture Was heated at 200 ° F for 3 hours finally obtained was measured in accordance with the parcel UCS test pieces Grains with compressive strength greater than 500psi....

39, the coated particles according to claim 38, wherein the 195 ° F, the maximum pressure of 4000psi, Minimum pressure 1000psi conditions for 30 cycles of cyclic stress test, the packet Leggings particles have a rate of less than 15% of the reflux.

40, the coated particles according to claim 38, wherein the coated particles having at least 50psi pressure Strength of rebound strength.

41, the coated particles according to claim 38, wherein the coated particles having a first pressure UCS Strength of at least 5% of the rebound strength.

42, the coated particles according to claim 38, wherein the coated particles having a first pressure UCS Strength of at least 10% of the rebound strength.

43, the coated particles according to claim 34, wherein the particles comprise a first resin coating, optionally Containing a second resin coating; wherein the first resin is selected from a phenol - aldehyde, epoxy resin, Urea - aldehyde, furfuryl alcohol, melamine - aldehyde, polyester, alkyd resins, phenolic Varnishes, furan resin, phenol resin and furan resin, and a combination of phenol, furfuryl Ethanol and aldehyde trimers;

Second resin is selected from phenol - aldehyde, epoxy resin, urea - aldehyde, furfuryl alcohol, Melamine - aldehyde, polyester, alkyd resin, novolac, furan resin, phenolic resin Fat and furan resin, and a combination of phenol, furfuryl alcohol and an aldehyde trimer; wherein The first set of the resin composition and the second resin composition may be the same or different.

Second resin is selected from phenol - aldehyde, epoxy resin, urea - aldehyde, furfuryl alcohol, Melamine - aldehyde, polyester, alkyd resin, novolac, furan resin, phenolic resin Fat and furan resin, and a combination of phenol, furfuryl alcohol and an aldehyde trimer; wherein The first set of the resin composition and the second resin composition may be the same or different....

Second resin is selected from phenol - aldehyde, epoxy resin, urea - aldehyde, furfuryl alcohol, Melamine - aldehyde, polyester, alkyd resin, novolac, furan resin, phenolic resin Fat and furan resin, and a combination of phenol, furfuryl alcohol and an aldehyde trimer; wherein The first set of the resin composition and the second resin composition may be the same or different....

The second curable resin coating contains at most the amount of the partially cured to a second curing Agent.

46, according to claim 33 wherein the preparation of coated particles, which comprises the steps of: First particle matrix preheated to 225-550 ° F; then mixed with the first curable resin, The substrate surface to form a first curable resin coating; Subsequently, containing a second curable then At least a monolayer coating of resin wrapped first curable coating.

47, according to claim 34, wherein the preparation of coated particles, which comprises the steps of: First particle matrix preheated to 225-550 ° F; then mixed with the first curable resin, The substrate surface to form a first curable resin coating; Subsequently, containing a second curable then At least a monolayer coating of resin wrapped first curable coating.

48, The method of claim 47, further comprising the steps of:

To the first curable resin coating on the added amount of partially cured up to a first Curing agent;

The second curable resin coating on the added amount of a second up to a partially cured Curing agent.

49, The method of claim 48, including:

(a) first particles of the matrix is preheated to 350-450 ° F, and then increase the amount of The uncured resin to form a mixture, the uncured resin is selected from Furan resin, phenol resin and furan resin, a combination of phenol and furfuryl Ethanol and formaldehyde trimer; Then, at 225-450 ° F under sufficient time for The mixture was stirred room, the resin matrix coated particles, spanning Lipid coated particles of the matrix;

(b) particles of the resin coated substrate in contact with the catalyst, the catalyst is selected from:

(1) pKa of the acid is less than or equal to 4;

(2) Water-soluble salts of polyvalent metal ions;

(3) pKa less than or equal to 4 acidic salts of ammonia or amine;

(c) are repeated at least once steps (a) and (b), to generate an intermediate wrap Pieces Grain products;

(d) then a certain amount of uncured novolac resin, an intermediate package Granular product and hexamethylenetetramine mixed.

50, The method of claim 49, wherein the catalyst is an aqueous solution of ammonium chloride.

51, The method of claim 49, wherein the resin is a resin increment of the total amount of 5 - 50 wt%.

52, The method of claim 49, wherein the particulate material is added to the resin mixture 0.01 to 0.5 wt% lubricant.

53, The method of claim 49, wherein the timing of the lubricant is added prior to the final use After the amount of catalyst, and the mixture before rupture.

54, The method of claim 49, wherein the steps of:

To the first curable resin coating on the added amount of partially cured up to a first Curing agent;

The second curable resin coating on the added amount of a second up to a partially cured Curing agent.

55, a treatment method for the formation, including the following steps of: applying the right formation Claim 33 coated particles and hydraulic fracturing fluid mixture, then in the formation fractures Department of the particles solidify.

56 A method of forming a wellbore filled gravel, which includes the complex of claim 33 Aggregate particles into the wellbore.

57, a treatment method for the formation, including the following steps of: applying the right formation Claim 34 coated particles and hydraulic fracturing fluid mixture, then in the formation fractures Department of the particles solidify.

58, a method of forming a wellbore gravel filling which comprises the complex of claim 34 Aggregate particles into the wellbore.

59 A coated particle, which comprises:

Particles;

Fully coated particles at least a first resin layer of a single layer;

Fully wrapped in at least a single layer of a first resin layer on at least a second tree Fat; wherein the coated particles having a first compressive strength UCS strength of at least 5% of the rebound.

60, particles of claim 59, wherein the coated particles having a compressive strength of at least 50psi Rebound strength.

61, particles of claim 59, wherein the coated particles having a first compressive strength UCS Strength of at least 10% of the rebound.

62, the coated particles of claim 59, wherein the 195 ° F, the maximum pressure of 4000psi, Minimum pressure 1000psi conditions for 30 cycles of cyclic stress test, the packet Leggings particles have a rate of less than 15% of the reflux.

63, the coated particles of claim 59, wherein the first amount of curable resin coating contains Up to the partially cured on the first curing agent;

The second curable resin coating contained in an amount up to the second fixing portion cured Agent.

The second curable resin coating contained in an amount up to the second fixing portion cured Agent....

The second curable resin coating contained in an amount up to the second fixing portion cured Agent....

The second resin is selected from phenol - aldehyde, epoxy resin, urea - aldehyde, furfuryl alcohol, tri Melamine - aldehyde, polyester, alkyd resin, novolac, furan resin, phenol resin And furan resin, and a combination of phenol, furfuryl alcohol and an aldehyde trimer; wherein the first A resin composition and the second resin composition may be the same or different.

66% E3% 80% 81% E6% 9D% 83% E5% 88% A9% E8% A6% 81% E6% B1% 8259% E6% 89% 80% E8% BF% B0% E9% A2% 97% E7% B2% 92% E6% 9D% 90% E6% 96% 99% E7% 9A% 84% E5% 88% B6% E5% A4% 87% E6% 96% B9% E6% B3% 95% EF% BC% 8C% E5% 85% B6% E4% B8% AD% E5% 8C% 85% E6% 8B% AC% E5% A6% 82% E4% B8% 8B% E6% AD% A5% E9% AA% A4% EF% BC% 9A% 0A% 20% 20% 20% 20% 20% 20% 20% 20% 20% 20% 20% 20% 20% 20% 20% 20% E5% 85% 88% E5% B0% 86% E9% A2% 97% E7% B2% 92% E5% 9F% BA% E8% B4% A8% E9% A2% 84% E7% 83% AD% E5% 88% B0225-550% C2% B0F% EF% BC% 9B% E7% 84% B6% E5% 90% 8E% E5% 86% 8D% E4% B8% 8E% E7% AC% AC% E4% B8% 80% E6% A0% 91% E8% 84% 82% E6% B7% B7% E5% 90% 88% EF% BC% 8C% E5% 9C% A8% E5% 9F% BA% 0A% 20% 20% 20% 20% 20% 20% 20% 20% 20% 20% 20% 20% 20% 20% 20% 20% E8% B4% A8% E8% A1% A8% E9% 9D% A2% E5% BD% A2% E6% 88% 90% E7% AC% AC% E4% B8% 80% E6% A0% 91% E8% 84% 82% E6% B6% 82% E5% B1% 82% EF% BC% 9B% E6% 8E% A5% E7% 9D% 80% EF% BC% 8C% E5% 86% 8D% E7% 94% A8% E5% 90% AB% E6% 9C% 89% E7% AC% AC% E4% BA% 8C% E6% A0% 91% E8% 84% 82% E7% 9A% 84% E8% 87% B3% E5% B0% 91% E5% 8D% 95% E5% B1% 82% 0A% 20% 20% 20% 20% 20% 20% 20% 20% 20% 20% 20% 20% 20% 20% 20% 20% E5% 8C% 85% E8% A1% A3% E5% 8C% 85% E8% A3% B9% E7% AC% AC% E4% B8% 80% E6% A0% 91% E8% 84% 82% E6% B6% 82% E5% B1% 82% E3% 80% 82

67, a treatment method for the formation, including the following steps of: applying the right formation Requires 59 coated particles and hydraulic fracturing fluid mixture, then in the formation fractures Department of the particles solidify.

68 A method of filling gravel to form the wellbore, which includes the complex of claim 59 Aggregate particles into the wellbore.

69 A coated particle, which comprises:

Particles;

Fully coated particles at least a first resin layer of a single layer;

Fully wrapped in at least a single layer of a first resin layer on at least a second tree Grease;

Wherein the coated particles have a coating each of more than 15% acetone extraction rate.

70, the coated particles according to claim 69, wherein the 195 ° F, the maximum pressure of 4000psi, Minimum pressure 1000psi conditions for 30 cycles of cyclic stress test, the packet Leggings particles have a rate of less than 15% of the reflux.

71, the coated particles according to claim 69, wherein the first amount of curable resin coating contains Up to the partially cured on the first curing agent;

71, the coated particles according to claim 69, wherein the first amount of curable resin coating contains Up to the partially cured on the first curing agent;...

71, the coated particles according to claim 69, wherein the first amount of curable resin coating contains Up to the partially cured on the first curing agent;...

73, the coated particles according to claim 69, wherein each coating layer has 15-30% of the Acetone extraction rate.

74, according to claim 69 for preparing particulate material, which comprises the steps of: First particle matrix preheated to 225-450 ° F; then mixed with the first resin, the base A first resin layer formed on a surface quality; Subsequently, then at least a second resin layer containing First resin coating wrapped coating.

75, a treatment method for the formation, including the following steps of: applying the right formation Claim 69 coated particles and a mixture of hydraulic fracturing fluid, and then within the fractures in the formation Department of the particles solidify.

76 A method of filling gravel to form the wellbore, which includes the complex of claim 69 Aggregate particles into the wellbore.

77 A coated particles from sticking point in the experimental determination of the melting point range of 200-300 ° F, Containing:

Grained matrix;

A first surface of the substrate particles, partially cured resin coating;

In the first part covers the surface of the cured resin coating a second, partially cured resin Coating.

78, the coated particles according to claim 77, wherein the coated particles have more than 15% acetone Extraction rate.

79, the coated particles according to claim 77, wherein the first resin is selected from (1) a furan resin; (2) phenol resin and furan resin composition; (3) phenol, furfuryl alcohol and acetaldehyde Trimer;

A second resin comprising a phenolic novolak and its corresponding curing agent.

80, the coated particles according to claim 77, wherein the coated particles and the ratio of the first gallon 12 pounds of particles KCl solution 2% KCl solution to form a mixture, followed by the mixture Was heated at 200 ° F for 3 hours finally obtained was measured in accordance with the parcel UCS test pieces Tablets having a compressive strength greater than 60 percent retention.

81, the coated particles according to claim 77, wherein the coated particles and the ratio of the first gallon 12 pounds of particles KCl solution 2% KCl solution to form a mixture, followed by the mixture Was heated at 200 ° F for 3 hours finally obtained was measured in accordance with the parcel UCS test pieces Reap the freedom of compressive strength greater than 500psi.

82, claim 77 for preparing coated particles, which comprises the steps of:

The first resin mixed with the particles of the matrix;

The first resin mixed with the particles of the matrix;...

The first resin mixed with the particles of the matrix;...

Wherein the step of curing the finished part, the first resin and the second resin have large Extraction rate of 15% acetone. ...

Wherein the step of curing the finished part, the first resin and the second resin have large Extraction rate of 15% acetone. ...

84 A method of filling gravel to form the wellbore, which includes the complex of claim 77 Aggregate particles into the wellbore.

84 A method of filling gravel to form the wellbore, which includes the complex of claim 77 Aggregate particles into the wellbore....

84 A method of filling gravel to form the wellbore, which includes the complex of claim 77 Aggregate particles into the wellbore....

At least a single full package substrate a first curable resin;

Fully wrapped in at least a first curable resin layer on the second layer may be at least Curable resin;

Wherein at least a first curable resin layer and at least a second curable resin layer Each of the coating has more than 35% acetone extraction rate.

86, the coated particles according to claim 85, wherein at least a first curable resin layer, and to Less curable resin layer of each of the second coating layer has a greater than 40% of the acetone extract Rate.

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